The US has vowed to catch the killers of American hostage Nick Berg who was shown being beheaded on an Arabic language website.
The images have caused widespread revulsion in the US.
His captors said they were avenging the abuse of Iraqi prisoners in US custody.
Mr Berg was a US civilian who had gone to Iraq to look for work for his telecommunications company.
The Bush administration has called his killers "enemies of freedom".
What do you think the wider impact will be? Will this affect coalition efforts in Iraq?
This debate is now closed. Read a selection of your comments below.
The following comments reflect the balance of the opinion we have received:
It's murder disguised as jihad, then it's the perversion of suicide and murder into martyrdom. And now we have ritual human sacrifice. There seems to be a synchronized Dance of Death occurring here...while America's image and honour are pushed toward disaster and one of the world's great religions is being dragged into the abyss by maniacs.
The brutal murder of Mr. Berg is sickening. But again I am sure that the anti-American crowd being fed by the media will find that America is to blame for Mr. Berg's death. Everything seems to be America's fault. I am shocked and saddened when I see the media is outraged over naked prisoners, but is relatively quiet when an innocent American worker is slaughtered. Shame on the media for its disgusting bias!
This murder was heartless and gutless. These men were not even brave enough to not show their faces. If they truly believed that these acts were just then they wouldn't have worn masks. This shows the true cowardice of these heartless killers. My prayers are with the Berg family.
William McDaniel, Hominy, USA
The whole situation is a Catch22 on the largest of scales. If we leave the region it will probably fall into a bloody civil war which will kill thousands of innocents. If we stay and try to help rebuild the region there will be more and more scenes like this.
Terrorists are not born but get created and I can't help thinking that this whole Iraq affair will end up not in rooting out terrorism, however it is defined, as intended but creating more of them. However much disgust expressed, and rightly so, at the Nick Berg murder, I can't help thinking that this is a price we will now pay for the arrogance of a handful of "world leaders" and their self serving agenda. This so called war on terrorism has meant this world a far more dangerous place than we could ever have imagined.
S Ghose, UK
Terrorists are using religion as a front to practice pure evil. I don't believe they understand or really care about their religion. I notice some people are putting it down to different cultures etc. Maybe this is partly true, but when it comes down to it, the terrorists know what they are doing is wrong, yet they still do it! Good people don't need to hide behind masks.
Some kill a man with a knife, and some kill children and women in their homes with 500lb bombs. If you want to show one, then show both. We should also condemn both. A sudden death is always better than a prolonged physical and emotional suffering and abuse.
Mohamed Daud, Kuala Lumpur
The real enemies of freedom are the liberal cowards of the west who are unwilling to confront the evil of terrorism with the force of good. Every shout of "Vietnam","get out now", and "arrogant Americans" only emboldens the hooded cowards in this sickening picture.
Rod Sturgeon, USA
This is much bigger than the Daily Mirror. The weight of evidence shows that abuse and ill treatment certainly took place, probably on a systematic basis. I am saddened that so many correspondents blame the messenger.
Mark Horner, Northumberland
More than a week after the Mirror published the photos why is there still no word from the government as to their authenticity? Is it because the reality is much, much worse? In any case, what right does the government have to withhold the Red Cross report? It is a non-governmental organisation funded by donations from us, the public.
CK Yoe, London UK
There is no excusing this sick act, but this should stand as a lesson for anybody who has no good reason to be in Iraq -- get out of there!
Perhaps if the worlds' media had let the 'Torture of PW issue' drop, instead of creating their own news then Nick Berg may still be alive. All these parties want coverage. By all means expose an issue but now people are dying because of newspaper and TV coverage of this situation.
Iain Warren, UK
If these killers are so convinced in the justification of their act, why do they feel the need to cover their faces?
Tony, Birmingham UK
Praising Allah while cutting off the head of an innocent man? Muslims all around the world should be outraged! The prisoner abuse had nothing to do with people acting in the name of God. Lets make that clear.
Michael, Pennsylvania, USA
Because of the illegal occupation in Iraq, people all over the world are giving in to their lesser nature, breeding hate and ignorance. People must ask for strength when confronted with such low minded examples of hate, as not to become part of that malignancy. All of us, no matter what creed or race, have to take responsibility for our actions and responses.
Larn P , Vancouver, Canada
The cycle of violence continues.
Norman, Kampala Uganda
I'm a Vietnam vet and it seems to me we're fighting another unwinable war, and at the cost of American lives both military and civilian. If we're there to win then let's get it done or get out. Why waste all these lives just for political posturing that's not serving any purpose whatsoever, other than the loss of precious lives?
It is totally beyond my comprehension how people can commit such acts of inhumanity. This video does nothing more than to fill the world with more hate for Iraq instead of just a few sick individuals.
As a veteran I see now more then ever why we CAN'T pull out now. If we do the terrorists win. They perform these despicable deeds hiding behind masks, to untrained civilians. They are not warriors, they are cowards who hide and don't take responsibility for their actions. They do these things to scare us and make us cower and not protect the people of Iraq who want us there. Pulling out would be the same as letting a school bully pick on the meek. To the family of Nick I'm sorry for your loss and you're in my prayers¿
Ghandi said: An eye for an eye leaves the whole world blind. The US soldiers have committed an unforgivable offence against Iraq, but this was not the way to counter it. This won't be over until both sides just admit that enough is enough.
Unfortunate that the innocent have to pay for the deeds of those guilty of masquerading their crimes as justice.
Burt Cummings, Sputnamburg, USA
I am tired of torture and death. I am tired of fanatical terrorists who, while cowardly hiding in hoods and caves, slaughter innocents with knives and airplanes in some vain attempt to force their ideology on peaceful folk; or worse, just for fun. I am tired of cowardly superpower leaders who, while sitting safe in their well-defended offices, send their youth into war in an ignorant attempt to force their own ideology on a culture they never bothered to learn anything about; or worse, just for oil. It takes far more strength to exercise restraint than it does to bomb or behead defenceless civilians. Terrorists and governments seem to all be weaklings.
Evan, Boston, USA
This just proves it! Actions taken by the Bush administration and it's allies to fight terrorism are doing exactly the opposite. It is breeding more hatred and incensing more people into sinking to new depths. Law of nature - every action has an equal and opposite reaction.
Will Deaver, Richmond, VA, USA
When you sow the wind you reap the whirlwind. Retribution for an ill conceived war plan will reap more grisly, barbaric events in Iraq.
Charles Crone, Mount Olive, NC, USA
Iraq. The new Vietnam. I've seen it all before. Stick your nose in the wrong place, you get it removed.
Alan Adelman, Memphis, TN, USA
I think killing this man was a disgusting display. To equate this sort of brutality, to the minor humiliation suffered by Iraqi detainees, is ridiculous. This man was not a soldier. He was just a guy trying to make a living.
Chris, Lochbuie, USA
Shocking, but not unexpected given the recent circumstances. But it was always on the cards something like this would happen given the fact that America do not understand the culture and psyche of anyone beyond their own front gate.
Interesting! The same as usual. So many comments providing a field of excuse for Islamic/Arab actions, no matter how terrible. America of course continues to live without excuse, confronts its abuses with shame and an open process. Here you actually have a man shouting "God is great" while he slaughters a human being - and where is the outrage from the clerics whose religion is being defiled? Just a deafening silence.
Ian Isemonger, Kochi, Japan
They are a disgrace to their religion and the freedom of society,
Harvey, Newcastle, England
I really hope justice caught up with these sick perpetrators of this murder. They are an abomination to all civilized people in this world! Show them no mercy!
Tony Lim, Singapore
We must have revenge. Those responsible must be captured and must be put to death.
Iain, Loughborough, UK
Now the US is determined to catch the killers. Now we will see again thousands of innocent being killed. There won't be any end to the violence.
As Americans, some of us are seeing for the first time the essence of war, in its unsanitized and pure state. War by nature is graphic, is poignant, and no matter how one tries to explain it away war does not play by rules. War is as erratic as the US rationale behind beginning this bloodbath in the first place.
Steve Sullivan, Washington, US
This whole thing is getting out of control. Nothing makes sense anymore. We should pull out all civilian contractors at once.
Mike, Los Angeles, USA
As a white convert to Islam I am disgusted and ashamed by the cruel beheading of Nick Berg, and only hope that the public will be able to recognise that Muslims worldwide are as shocked and appalled by such acts as everyone else.
Sam Taylor, Marlborough, UK
I am an Iraqi and I want to make it clear that al Zarqawi is a Jordanian wahhabi Sunni. This man Zarqawi is the ultimate evil.
Sahab Abdul Hadi, Glasgow, UK (Iraqi)
What is Bush waiting for, if he doesn't pull out now, this is only the beginning of what is to come.
Ellen, Minneapolis, US
Just appalling. I was repulsed by the images from Abu Ghraib prison but this is even worse. It's always the innocent that suffer in this repugnant world. And in this sick digital age this awful film will be watched and enjoyed by millions of armchair sadists all over the world for decades to come. What a brutal time we are living in. Nobody here at work feels an ounce of compassion for this man or his family. And as for the animals who did this - they had an opportunity to show that they were better than their occupiers. More humane, more moral. They should have treated this man with respect even though the Yanks had abused their men. Then the world would have rallied to their cause. But now they've lost all sympathy.
M Maguire, UK
It is heartening to read the comments from Muslims declaring this to be an atrocity and against their religion. An act like this stands on it's own and cannot be justified by any other.
Scott West, Chicago, USA
I completely disapprove of any loss of innocent live. That is the reason I was vehemently opposed to the illegal war against Iraq. My prayers are with all the families who lost their innocent love ones including tens of thousands of Iraqis.
Enough is enough. Bush's administration needs to understand that innocent killings bring more innocent killings and terror. The only difference between the Bush admin and the AL QAEDA admin is that the killing session was relayed on the internet. We don't know what is US hiding or has hidden so far.
Ashfaq, Leeds, UK
Mr. Berg went to Iraq alone on his own volition to make money. News reports here in the US have said he was warned by the occupying forces to leave for his own safety, but he refused. He took a calculated risk because he wanted to make money, and lost. Let's save our sympathy for the people who really need it: the 19-year-old kids who joined the Army because it offered them college tuition money and are now thrown into the middle of the violence and anger. Mr. Berg had a choice - they don't.
Amanda Reno, Minneapolis, USA
This is unbelievable human behaviour. I can't believe this is happening in 2004. As a Muslim I can only say, we are not allowed to touch an innocent civilian!
Imran Azim Butt, Doha, Qatar
Show the video. The West needs the reality therapy to cure its apathy to this increasingly deadly world war in which the next battle hit could be Athens, London, Paris, Frankfurt, LA or San Francisco.
Fr. Jim Anderson, MSA, Santa Maria, CA, USA
This is deplorable. No religion, culture or society can defend this action. US administration's policies in the Middle East have created this savage hatred against all Americans though they have nothing to do with the policies of their government. I, with no reservations, condemn this act. I also condemn the US policies in the Middle East which have made this world a very unsafe place for an average hard working American.
Abdullah S. Jafari, Houston, Texas, USA
Pull out and leave them to it. No matter how long western forces are in Iraq, eventually, it will return to the same as it was before Saddam was removed. Some things just don't change.
Adam, Manchester, England
God rest his soul. I hope he didn't see it coming. These people can get really nasty because they are desperate and have nothing to lose because their leaders lack the guidance to lead their people to a better world even with a varying religion to the rest of us. Salute' to the men and women who continue to fight and believe that there will be a new tomorrow for Iraq.
Sue Bateman, Australia
I am a Muslim and I am shocked at the killing of an innocent civilian. This is a very ugly murder and these people should be punished. The atrocities of some American soldiers in Iraqi jails doesn't give anybody an excuse to murder civilians.
Riad El Fadel Raad, Tripoli, Lebanon
Yes this is a disgusting outrage by a bunch of inhuman thugs. Unfortunately the same can be applied to the US military.
It is time to take off the gloves with these people. Will there be a 'commission' to deal with this abuse?
Charles Bell, USA
Very sad but surely not unexpected. If the coalition does not get rid of their pride and arrogance then the enemy will humble them.
David, Portadown, N Ireland
Is it possible that these men consider Mr Berg's death sacrificial and if so then honourable even if we see it as murder. Do they see what was done to prisoners by US troops as worse than death? Is this a matter of perspective?
Matthew Iles, Naples, FL, USA
Of course, I reject this barbarian murder and I cannot find any reason that justifies it, but what did everybody expect? Democracy and freedom for the Iraqi people? There is a war in Iraq, and wars only bring anger, death and brutal acts like this horrible murder or the abuses in Abu Ghraib jail. If we want to stop the violence in the Middle East, the USA and its allies must withdraw their troops and let the UN take control of the situation. Only with international agreements will all this chaos be sorted out.
Leandre, Barcelona, Catalonia
From BBCArabic.com: Can these criminals really be Arabs and Muslims? Do they pray in our mosques and speak our language and suffer like we do? Their hearts have turned into stone. What we need is tolerance and wisdom, not blind revenge. Blood cannot be washed off with more blood.
Mohamed Bin Bandar, Mecca, Saudi Arabia
From BBCArabic.com: This is a heinous crime and those who committed it are like a disease in our Islamic societies. It is absurd to compare this crime to the abuses in Abu Ghraib prison. Those who justify this crime have lost touch with reality and are only fooling themselves.
From BBCArabic.com: I totally reject this brutal crime against an innocent hostage, but I think the US has pushed the whole of the Middle East to the brink of disaster.
Abdullah Almasri, Cairo, Egypt
From BBCArabic.com: This does not represent our moral and religious values. These criminals are harming Islam and the image of Muslims all over the world. My heart goes out to Berg and his family.
Fadi Morestani, Riyadh, Saudi Arabia
From BBCArabic.com: What happened is totally unacceptable, but violence breeds violence and every action will have an opposite reaction.
Abul Fedaa, UAE
Revulsion, for sure, another step down the stairs to primitive times. The argument that the killers needed an excuse does not hold water because they do these atrocities for ideological, even vague reasons. What the hell this sweet Mr Berg did to them or to their country? Nothing, on the contrary he was there to help their country get back on its feet.
Aharon Fattal, Vielsalm, Belgium
The murderers of this innocent, defenceless civilian look for any excuse to kill. Don't be fooled, they are not killing for any reason, they just enjoy murdering.
Phil, Bath, UK
There is no need for the warring parties to de-humanise each other. They are doing a damn good job of de-humanising themselves
John Dorsey, Cornwall, NY, USA
Nick Berg's life could have been saved only if the invading soldiers were prohibited from carrying cameras.
Girish, Cambridge, UK
Complete disgust and anger at the action of such cowards who are prepared to murder from behind and masked so as not to reveal themselves
Malcolm Reynolds, London, England
Frankly, I see no difference in this brutality compared with the brutality of some of the troops, just a rather different way of doing it. Yes, it's tragic, but what on earth do we expect when we cannot behave in a civilised way ourselves? This won't be the first
Jean, Devon, UK
Hopefully, even those who talk about "respecting other cultures" will condemn this. Sadly though, I expect the anti-US xenophobes will be out again, and once again we'll hear that absolutely any atrocity is OK when carried out against Americans.
Alex Swanson, Milton Keynes, UK
I can only hope that the Iraqi people condemn this atrocity as virulently and as prolifically as the British Press condemned the torture photos. We must remember that there should be no distinction between the occupier and the occupied when it comes to acts of such barbarity and savagery.
Chris F, Essex, UK
I'm sure this will push the coalition into short term action against these 'barbarians'; however, if the Iraqi public do not stand up to these groups of militia, then they will become Saddam's replacement. The question should be what do the Iraqi people want -democracy or Saddam with a different name?
John, Rehovot, Israel
It is sad that a person who is not involved in anything had to pay the price for other's mistake.
Lets face it, Mr Berg knew the dangers of Iraq but nevertheless went there to make money. He wasn't a worker, he ran a business and he took the risk and paid the ultimate price. Lets hope the US doesn't go in now and kill hundreds of innocent civilians with helicopter gunships and 400lb bombs, like it did in Falluja after the 4 US civilians were killed there.
Rob Kelly, UK
This is an outrage, this is sick. Whether you support the war in Iraq or not, the international community cannot accept this killing lightly.
From BBCArabic.com: This is a disgusting crime. We denounce this terrorist act perpetrated by sick minded people.
Zaid Diauddin, Iraq
From BBCArabic.com: This man "Zarqawi" is the ultimate criminal and represents only himself and the rogue mob that he leads, but the will of the people will prevail.
Abul Kassem, Musul, Iraq
From BBCArabic.com: If the victim is an innocent civilian, then this is a crime against humanity that should be condemned by everyone and the person who committed this crime should be brought to justice.
From BBCArabic.com: I think that what this Zarqawi did is extreme savagery and sadism. This has nothing to do with Islam. These people use Islam to conceal their vicious aims.
From BBCArabic.com: What appeared in this tape is less than what the Americans did to Muslims in the prisons of Iraq.
From BBCArabic.com: A stupid act that does not represent Islam or Muslims.
A Muslim, Washington, USA
From BBCArabic.com: I imagine the West will mobilise its mighty media machine to accuse Arabs and Muslims of terrorism, as usual. Just wait and see.
Nawaf Bin Mohamed, Riyadh, Saudi Arabia
It is now time for us to pull out and leave them to it.
Enough is enough.
There is no justification for this atrocity. But Bush with his medieval world view should not at all be surprised to get a medieval response like this.
Martin Brune, London, UK
Now see what the media's fascination with showing only the bad side of this war has done? I blame the media for this death! Show the good that has come about rather than only the bad and help prevent these events!
Tony Kenny, Cumbria, UK
It is now clear what sort of enemy the coalition forces are up against!
Len Williams, Brighton, UK
This is absolutely unbelievable, that in this day and age things like this can happen. This just goes to show how disturbed these terrorists are, and why we need to hunt down and destroy every last one of them