Thousands of people are stranded in New Orleans without food or water after Hurricane Katrina - a fierce mass of winds swirling at 155mph (250km/h) - caused widespread devastation to the region.
President Bush is visiting the area after acknowledging the initial response was "not acceptable" and pledged to restore order in the city.
BBC correspondents report on the latest developments from the worst-hit areas of Louisiana and Mississippi.
Friday Sept 2
Adam Brookes, New Orleans, LA : 17:24 GMT
Just before dawn a resounding thud echoed across the centre of New Orleans. A paint factory had apparently exploded close to the river. The city was suddenly shrouded in acrid smoke.
Among the thousands of desperate people at the city's convention centre waiting for evacuation there was near panic. Many thought the floodwaters were coming and they'd have nowhere to run.
It was the fourth night they'd passed there, out in the open waiting for buses to take them out of the city; that just never come.
One army veteran, sick with diabetes, with no medications, asked me why if the United States is capable of invading a country half a world away, wasn't it capable of driving him 10 miles across the river.
It was as if in his mind the very idea of Americanness and citizenship was being betrayed.
Matt Frei, New Orleans, LA : 17:05 GMT
The historic French quarter is reduced to a disaster zone and is beginning to look like a war zone.
Some people have lost everything and are now beginning to lose their minds.
This is the wretched home to thousands, most black but all incredulous they have become refugees in their own country, and have received no help in five days.
We met a woman with a baby who is seven weeks old, who said she had nothing. And occupants of a nursing home, stranded in their wheelchairs, who have no medical help.
It gets worse. We saw a store room at the back of the centre, now a makeshift morgue. Two bodies were left to rot outside in the baking sun.
A helicopter arrives and the supplies are left on the ground for the desperate to fight over. The police are getting edgy - there is a complete breakdown of law and order.
If Bush set foot here he'd see something which no longer resembles the country he was elected to govern.
Adam Brookes, New Orleans, LA : 16:00 GMT
The Governor is attributing the worst of the violence in the city to drug addicts who have looted gun shops and are now prowling the city to get a fix any way they can.
There's a very aggressive police presence. They don't stop and talk to the refugees at all and they don't communicate with them. They just speed by in their pick up trucks and their cars pointing shotguns out of the window as they go. It's quite extraordinary behaviour. And these desperate people are waiting for evacuation. The police behaviour makes them all feel like suspects.
Every now and again a military helicopter comes in, it hovers over a car park and soldiers throw out big boxes of bottled water and food ration packs and then a great tide of young men come running in and start fighting for the food. This means that the most vulnerable people, the sick and elderly, many families don't get a shot of the food coming down. There are five corpses there, at least from what we've seen today, it could be a serious development.
President Bush has just been in Alabama looking at the devastation there. He's going to take a flight over New Orleans this afternoon. He's not actually going to touch down here because of the security situation. He's called the rescue effort unacceptable. He seems to be now in a growing amount of political trouble. Petrol prices are rising all over the country the media are tearing into him.
Adam Brookes, New Orleans, LA : 15:25 GMT
I went to the Superdome and there are about 15,000-20,000 people. The pace of evacuation there is unbelievably slow. We seem to see columns of buses going in but the number of people going out does not seem to change. There are helicopters which throw food and water out and men fight over the relief aid. So the elderly and mums and pregnant women don't get anything. It's an extraordinary situation.
At either end of the centre are armed troops and police but nobody is walking up and down the crowd that are outside. They are not trying to figure out who to give water to, baby formula, or antibiotics. We discovered this morning that a number of children are starting to go down with diarrhoea which I think may be the most serious development overnight.
Elsewhere at the Convention Centre, there isn't a bus in sight. The only thing you see out of 2,000-3,000 people is police cars going through pointing shotguns. These are unbelievable conditions. Words begin to fail me.
Daniel Lak, Biloxi, MS : 15:25 GMT
From his helicopter in the air and on the ground, President Bush will see the immense devastation wrought by Hurricane Katrina. He's expected to meet some survivors and talk to local officials. There's hope that his presence here on the Mississippi coast might add impetus to relief efforts which some survivors say have been inadequate.
The head of emergency management here has appealed for patience and has pointed out that lack of electricity and telephones is hampering his work as well.
Some areas of the coast have had power restored, police and the national guard say they're getting looting under control and deliveries of fresh water and ice are supposed to begin shortly.
Matt Frei, New Orleans, LA : 14:39 GMT
Thousands of refugees, and I can call them that, because they are living like refugees in their own city, mainly African Americans, held up in a convention centre down the road in appalling conditions. The panic amongst them must have been tremendous. These people have been waiting to be evacuated for four days now.
There was a Walmart looted just a couple of days ago and every single gun in the gun section of the shop had gone. There is so much looting going on people are very scared.
If you go to this convention centre where thousands of people are held up they were desperate. They took us to one area where they had taken the four people who had died just yesterday. No one had come to take these bodies away they were just lying there.
It is total mayhem. I have been to many disaster zones in Asia and a few in Africa and I must say considering the resources available here and all the rhetoric we've heard from Washington the situation here is much worse than comparable situations for these sort of crises in the Third world. It is quite frankly an indictment.
Adam Brookes, New Orleans, LA : 14:20 GMT
We understand President Bush will land in Mobile, Alabama and look around there.
He's not going to come to New Orleans, but fly over and take a look.
You have to wonder how much concern there would be for Bush's security:
There is considerable anger in this city now - the situation is desperate for tens of thousands of people. There are 15,000 - 20,000 people inside the Superdome. The pace of evacuation is exceptionally slow.
In the convention centre there are another 2,000 - 3,000 people who are in atrocious conditions. People are starting to get diarrhoea. If we start to see outbreaks of disease the situation will deteriorate very rapidly.
I think people here would tear Bush apart if he came here, verbally if not physically.
But Bush has to show his face, be visible and show leadership.
I am beginning to feel this could be a very serious political moment for him.
Oliver Conway, Washington DC : 14:15 GMT
President George W Bush said he was travelling to the devastated region to reassure those affected by Katrina that the government would do everything necessary to get the situation under control.
He said current conditions were unacceptable, but millions of gallons of water and millions of tonnes of food were on their way.
Daniel Lak: Biloxi, MS : 13:25 GMT
I am in a small boutique mall alongside the casino strip in Biloxi. A week ago, shoppers would be looking at trinkets to buy. It was under water and the ocean is a good 300 metres away.
It is natural for people dealing with such a disaster to want aid to get to them immediately. They think their problems need to be taken care of. When it doesn't arrive, resentment builds. The people here think it has taken a long time to even mention them.
I was in a place close to Gulfport and there were just a few soldiers and a few emergency management people. The big hope here is that President Bush's visit will speed things up.
Jon Sopel: Gulfport, MS : 13:15 GMT
The hurricane has taken its toll on the lives of the people in this city. Thousands have been made homeless. They are desperate for help and there is the security situation.
President Bush will arrive here in the next couple of hours. It will be interesting to see what kind of reception he receives when he gets here.
It seemed strange when we heard there were plans being made to evacuate people from New Orleans. This is a part of the world which is used to seeing hurricanes and tornadoes. But it turned out to be something of an under-reaction as events have proved.
You can see magnificent plantations and old buildings being swept away. There are emergency helicopters flying in and bringing aid to as many people as possible.
Jon Sopel: Gulfport, MS : 12:30 GMT
There is so much to do here. There is so much to clean up. There are thousands of people living here without water, without electricity, without fuel in their cars so that they can get out. In the meantime, the towns have become magnets for looters.
This is all adding to the sense of insecurity and impatience that something should be done. They have had two or three days to do it. And there are people complaining that there are thousands of national guard who would normally be in this state but are in Iraq.
When President Bush comes here, he will see the scale of the destruction. All along the coast, you will see scenes of devastation. It really is a shocking sight.
It will bring home to President Bush the urgency of the situation and how much needs to be done. They will need to rebuild, find jobs for people, but immediately they need food and water. They also need shelter and medical supplies.
Alastair Leithead: New Orleans, LA : 12:20 GMT
The evacuation effort is due to continue today but there are still many angry voices criticising the government for not providing them with enough emergency food and water supplies while they wait for the buses to arrive.
Jamie Coomarasamy: Baton Rouge, LA : 12:12 GMT
Along the US gulf coast, the picture of devastation is becoming clearer and bleaker. The wreckage reveals no clues as to why Katrina struck so hard.
There is a desperate search for any news about who it took away and who it spared. Predictions remain in the thousands, but an accurate figure may be some way away.
For those who did survive, life as they know it is destroyed and for the moment is hard to endure.
Still US refugees pour out of the area into surrounding towns like Baton Rouge. Shelters like these are mushrooming across the south of this country but the help they can give is only temporary.
Jonathan Beale: Washington DC : 12:10 GMT
President Bush has failed to reflect the mood of the country. He has failed to provide the kind of response that Americans expect. There is a lot of anger directed at the President in the country at the moment. He is going to leave the White House in the next hour. He will tour the disaster area. But people want more than sympathy from the President.
The Mayor of New Orleans says he wants action and not press conferences. Americans want the President to take control like he did, act like he did, in the aftermath of the attacks on September 11th.
There are now 1400 national guard troops arriving in New Orleans each day over the next few days. This is just in one city. Washington authorities say people will notice a show of force in the area. There will be a change. Hundreds of people will be moved out of refugees and evacuated out.
But that doesn't answer the question of why it has taken so long. And a lot of American commentators are saying - well these are scenes from the developing world rather than the world's only superpower.
David Loyn: New Orleans, LA : 12:05 GMT
They must have thought it could not get any worse. A new horror for New Orleans struck in the early hours - loud explosions possibly in a chemical plant, followed by intense fires.
Military helicopters have begun to take people out of the Superdome. For now officers have to select the most needy cases for evacuation, and they say they will get everyone out within two days.
Too much of their effort is spent not rescuing survivors but chasing looters.
If it weren't for the water this could be Baghdad, with troops wearing body armour, trying to regain control from armed gangs.
Bodies are crudely wrapped where people died. These are the poorest, who couldn't leave the hurricane, and now have nowhere to go.
In a hospital the most needy were lined up for evacuation. They waited, but the promised helicopters didn't come.
The world's richest country is not able to help its sickest people.
Alastair Leithead: New Orleans, LA : 11:52 GMT
There's a huge plume of smoke over downtown New Orleans.
After the explosion early in the morning at what is thought to have been a paint factory there were a short series of blasts shortly after 0430 local time. Early reports suggested it may have produced toxic fumes but the latest information is that the fire is merely threatening to spread to railway containers, thought to contain certain toxins.
The uncertainty over what happened and how serious the fire was is a good example of how poor communications are across the city, which is still without power.
The evacuation effort is due to continue today but there are still many angry voices criticising the government for not providing them with enough emergency food and water supplies while they wait for the buses to arrive.
Conditions in the various shelters are deteriorating. A number of people have already died.
Bill Turnbull: Biloxi, LA : 09:26 GMT
What is extraordinary about this storm is it's unimaginable power.
There are so many objects that have been picked up and thrown to the ground as if by an angry child. There is a generator next to a car. There is also some kind of straw mattress. An office chair. There are some paper cups on the ground. And there is some kind of waste paper bin. And then just above it a motorbike.
Around the corner in Biloxi's Hayes Street, I met some neighbours taking stock of their new situation.
I ask them what they are doing now.
A man tells me. "We're just taking it one day at a time. It's all we can do. I've got about five inches of mud in the house. The appliances are all ruined, the clothes, everything. All destroyed.
I ask him and his friends sitting with him if they have had any help from the authorities yet.
"No. All they have been doing is patrolling this area and that's it."
"They are trying to feed the people in the shelters. Giving them oxygen and stuff but we are hungry too," another man says.
"I understand that but I believe they should have more mobility. They should help more people rather than dealing with certain sections. Everybody needs help," his friend says.
And if you are here in Biloxi you do need help.
We found Sharon on a lonely road. She was still looking for lost friends. "This is terrible. It's terrible man. It's the aftermath, man. The reality has set in. It is just too much."
I wish her good luck and hope she stays safe.
She says thank you.
Jamie Coomarasamy: Baton Rouge, LA : 06:45 GMT
With every day the level of desperation here is rising. Thousands of people are still trapped inside New Orleans in a city where the authorities appear overwhelmed by the scale of the disaster.
Like many of the people living in unsanitary and dangerous conditions in the city, local officials are now pointing fingers, in their case at the federal government.
The head of New Orleans emergency operations described the relief effort as a national disgrace. He asked why America can send massive amounts of aid to tsunami victims but can't bail out his city.
Meanwhile, thousands of national guardsmen are due to arrive in Louisiana from across the United States to try to stem a tide of lawlessness which threatens to leave scars on the community long after the floodwaters have receded.
Daniel Lak: New Orleans, LA : 04:45 GMT
The authorities in the state of Mississippi say they won't have extra personnel to make special security arrangements for the visit of President Bush to the storm-ravaged Gulf Coast on Friday.
Secret service and other federal agencies are expected to compensate for that. All police and law enforcement officials in this area are needed for flood relief operations in the wake of Hurricane Katrina.
President Bush will see the massive floating casinos that have been hurled up on shore, thousands of smashed homes and downed power-lines, and perhaps gatherings of homeless people, for there are many of them here.
The president's handling of the crisis so far has been criticised by some local people in this area, who've told reporters they thought he should have done more - and sooner.
Politics aside, the president's visit should help speed up the rescue operation, which many here feel has been too slow to get started.