British Muslims are being urged by community leaders to help safeguard the UK from a terrorist attack.
The Madrid attacks killed 191 people
The Muslim Council of Britain has taken the unprecedented step of sending letters of appeal to every mosque in the country.
Hundreds of thousands of special booklets are also being printed advising Muslims to be vigilant, in light of recent threats.
The move comes following the Madrid bombing which killed 191 people.
The letters urge preachers to give correct Islamic guidance and to prevent criminals from infiltrating their communities.
They also call on Muslims to report any suspicious activity to the authorities.
It states: "Islam categorically forbids violence and killing of innocents, let alone indulging in violence which can cause death and mayhem."
Mainstream Muslim leaders fear fringe elements are using political struggles to mislead young people.
Sermons will be delivered on Friday saying terrorism has no place in Islam, while booklets will remind Muslims of their obligation to help safeguard Britain's security.
Iqbal Sacranie, Secretary General of the council, told The Times: "There is a letter going to mosques across the country bringing to their attention the concern that has been expressed of an immediate attack taking place in the UK.
"It is important that we exercise vigilance in terms of fulfilling our duty. If there is anything we become aware of, it is our duty to ensure that this is reported immediately to the police. We will not tolerate terrorism."
BBC religious affairs correspondent Martha Doyle said the MCB is acutely aware that recent attacks, such as the Madrid bombing, are undermining their community and putting everyone in danger.
The move has been welcomed by Scotland Yard.
Fifteen people are still being held in connection with the recent Spanish attacks.
Ten bombs exploded on four trains in the rush hour on 11 March.
Metropolitan Police commissioner Sir John Stevens admitted that a terror attack on London was inevitable shortly after the Madrid blasts.
While all Muslims of course condemn terrorism in all its form we should not forget the role of the media in shaping peoples perceptions. The constant and inaccurate references to 'Islamic' or 'Muslim' terrorists risks demonising and alienating the Muslim ummah (community) worldwide as a whole. Terrorist acts are contrary to the word of Allah and the Sunnah (way) of his Messenger (peace and blessings be upon him) and as such no act of terrorism is 'Islamic' and no terrorist is a Muslim. The MCB should spend more of its time trying to change the media's prejudiced portrayal of Muslims and Islam rather the patronising the Muslim community of this country which it claims to, but does not, represent.
Jonathan Marshall, Oxford
The first positive step towards a peaceful solution.
Paul Brown, Reading, UK
Credit must go to the MCB for this move. It is not easy for the law-abiding Muslim majority in this climate of Islamic terrorism. However this sort of action is just the sort of thing that will reassure the general public that the Muslim community is also doing all it can to combat terrorism. This in turn will help make the Muslim community as a whole feel less persecuted.
I am a Muslim and I consider myself to be a mix of the East and West culture. This can mean at times I feel ousted by both sides and fall right in the middle into no-man's land. Regardless of this predicament I will always say what I consider to be right and fair. I am pleased to hear the Muslim Council of Britain has taken the unprecedented step of making an authoritative voice across Britain. I believe strong, sensible and single leadership for Muslims is what is lacking. In this event it shows to the rest of the country we don't agree with terrorism.
Khalid Hashmi, Luton, Bedfordshire
An excellent move by the Muslim community. But why has it taken so long for such action to be taken? Nevertheless, it is a positive move that should be applauded.
Those who carryout such atrocity in our society are not religious people. In Islam, Christianity or any other faith killing is totally forbidden. If any person commits an act of terrorism they are outside and against their faith and should not be branded with the religion. The holy Koran clearly states "If you kill an innocent man, it is as though you have killed the entire humanity".
Saleem Haque, Liverpool, England
This letter by the Muslim Council is a wonderful step and will do much to repair community relations. There is a problem in this country. It is a problem for all communities and the Muslim community should be applauded here for finally taking action and not setting itself apart.
Andrew Williams, St Albans