One man is helped to finally escape the nightmare
The relief operation on the southern coast of the United States is now in full swing, with troops bringing food and water to some of the thousands of stranded people in New Orleans and major evacuation plans nearing completion.
President George W Bush has cleared his diary for the coming week to oversee relief operations, amid mounting criticism of the aid effort, and is due to visit the area again tomorrow.
BBC correspondents report on the latest developments from the worst-hit areas of Louisiana and Mississippi.
Sunday Sept 4
Alastair Leithead, New Orleans, Louisiana, 2357GMT
The shooting took place on a bridge in New Orleans between the Mississippi river and Lake Pontchartrain.
There were contradictory reports at first but piecing together accounts from the army and police, it seems a number of army corps contractors were crossing the bridge when they were fired upon by a group of armed men. The police then returned fire.
There's confusion over the casualties, with some reports saying eight of the gang were shot and five or six were killed, and other sources saying six people had been injured but with no word on fatalities. It's an indication perhaps of the poor communications in this disaster-struck city.
Since the hurricane the majority of the police force were reassigned away from the search and rescue effort to patrolling the streets.
There have been clashes between the authorities and armed gangs and there was a feeling that lawlessness was creeping into the chaos left by the storm.
Heavily armed police and army patrols have been very visible on the streets over the past few days and there was talk of both martial law and a shoot-to-kill policy for looters.
Alastair Leithead, New Orleans, Louisiana, 2301GMT
Police in New Orleans say they have shot and killed a number of people who were seen carrying guns in the city. A high-ranking police officer said either five or six people are thought to have been killed.
There's been a huge emphasis on security and maintaining law and order in New Orleans since the days after the hurricane when a feeling of lawlessness seemed to spread around the city.
There was talk of a shoot-to-kill policy for looters and of martial law and a lot of the search and rescue effort was redeployed on security.
The killing by police of these five or six people today on a bridge between Lake Pontchartrain and the Mississippi river is the latest in a series of confrontations.
The second-in-command of the force here said a group of around eight people were seen. All appeared to be armed, he said. But as yet there are few details of the circumstances in which they were killed or who fired the first shot.
Most of the city has now been emptied of people as the evacuation of New Orleans nears completion
Jamie Coomarasamy, New Orleans, Louisiana, 2152GMT
Donald Rumsfeld came to see for himself the work that the troops are doing. The US Defence Secretary toured a medical facility that's been established at New Orleans airport and he held high-level meetings to coordinate the relief and evacuation efforts now in full swing.
Mr Rumsfeld spoke of the magnitude of the flood damage, calling it an utter disaster of historic proportions. It will take weeks, months, even years, he said, to restore New Orleans to normality.
Inside the city itself, most of those who want to be evacuated have now managed to leave but in many neighbourhoods, especially those where there is less flood damage, there are people who are determined to stay, despite the lack of power and provisions.
Michael Voss, UN Headquarters, New York, 2122GMT
The United Nations first contacted the Bush administration with offers of assistance within days of Hurricane Katrina striking the Gulf coast. On Sunday the UN announced that their offer had been accepted.
Relations between the Bush administration and the UN have been strained for several years. This past week alone there's been friction over US attempts to push through major changes to a reform package ahead of this month's world summit.
But the humanitarian needs of the hurricane victims have forced a rapprochement. It's not so much funding as expertise that the UN is likely to provide.
After decades of coordinating major relief operations around the world, the United Nations has a large pool of experienced staff, many of whom were placed on stand-by this week.
A small team has now been dispatched to the USAID Hurricane Operations Centre in Washington to assess how best to help the emergency effort.
The World Food Programme, the World Health Organisation, UNICEF and the High Commissioner for Refugees are all ready to provide help if needed
Daniel Lak, Bayou La Batre, Alabama, 2056GMT
The first thing that Condoleezza Rice did in this town, just at the eastern edge of the storm's impact, was to visit a relief centre and pack a box of supplies, with the television cameras rolling, of course.
The Bush administration has sent its black secretary of state here with a one-item agenda, defend the administration against charges of racism and inadequately responding to Katrina's devastation. Miss Rice, speaking after touring the centre, did just that.
There's no doubt that the government is taking the charge of racism very seriously indeed. President Bush is returning to the region on Monday, no doubt to make similar denials.
Yet in Mississippi, the poorest American state and the one with the highest percentage of black people and among the scattered population of New Orleans, the perception still exists.
People had to wait a week for relief, it's thought, because they were neither well off nor white. Mr Bush's Democratic opposition in Washington looks set to make the crisis over Katrina a major partisan political issue.
Daniel Lak, Bayou La Batre, Alabama, 2014GMT
It's a measure of the extraordinary pressure on the Bush administration over the issue of race that the secretary of state, who usually deals only with foreign affairs, was sent to Alabama to defend her government's record.
Condoleezza Rice said that she, as a black woman and a cabinet minister, did not believe that race was in any way involved in what has already been acknowledged by President Bush as an unacceptable relief operation. She said it was about Americans helping Americans.
As for the slow pace of response, Miss Rice said that the hurricane was the worst natural disaster America had ever faced.
She and defence secretary Donald Rumsfeld have been defending the administration in the storm-hit region and President Bush is to make a second visit tomorrow, again to address concerns of racism and the inadequate response.
Matt Frei, New Orleans, Louisiana, 1803GMT
New Orleans has drowned in the water that surrounds it, the mighty Mississippi now rules the street here. The Big Easy has become a big stink, populated by the ghosts of life before the hurricane. This is now a Venice from hell.
On Cleveland Avenue, we found the remaining guests in what used to be the Park Plaza hotel, undiscovered until yesterday. Safe on the rescue truck the women give thanks to God for life, they tell of using flash lamps at night to try to alert the rescuers. For the last couple of days, there were 500 people there.
Wherever you look, the traumatic rubs shoulders with the bizarre, the sheriff turned gondolier, the Japanese photographer up to his belly in water, the woman in curlers passing on the rescue vehicle. Later we meet the lady with the curlers on the way to nowhere, out of town, anywhere and still thankful for life.
On the motorway flyover, we find crowds of people seething with anger, in 100 degree heat. They have been there five days. Most of them are black and poor, America's underclass.
Driving down Interstate 10, it is deserted apart from the ambulances and feels like a war zone. The misery here is on a panoramic scale. This story started with the fury of wind and water, who knows where it will end.
George Alagiah, New Orleans, Louisiana, 1648GMT
I'm standing in the heart of the city, where the bars were, where the jazz clubs were, this is where the thousands of tourists came every year. Now all you see is a few emergency workers and what's left when people left the city.
To my right, a clock - it stopped just before 12, when Hurricane Katrina struck.
Jamie Coomarasamy, New Orleans, Louisiana, 1640GMT
Law and order has returned to the streets of New Orleans and with it, some of the few remaining residents of this devastated city. They have been without food, water and power since Hurricane Katrina struck. But the squalor and lawlessness of the temporary shelters here had convinced them to remain at home.
Now, those centres which were crammed with abandoned people have been abandoned themselves, leaving behind huge debris-strewn rooms filled with the sights and smells of a desperate existence.
On the main interstate highway, speeding convoys of emergency vehicles weave in and out of small groups of people pushing shopping trolleys filled with as much of their goods as they can carry, many desperately searching for a lift to safety...
And so, one of America's greatest, most vibrant cities, is emptying, as the search for the living here increasingly becomes a search for the dead.
Jamie Coomarasamy, New Orleans, Louisiana, 1510GMT
As the US military continues its attempts to mend this broken city, the remaining residents of New Orleans are emerging from their homes.
Although some have been without food, water or power for more than six days, many people have remained behind their doors, perhaps from fear of entering a city where lawlessness was rife.
The two main centres where people had been gathering have now been evacuated, leaving behind debris-strewn rooms filled with the sights and smells of a desperate existence.
Daniel Lak, Gulfport, Mississippi, 1304GMT
Mississippi was already America's poorest state and Hurricane Katrina has dealt its economy a vicious blow. But more than that, the human cost of the storm has been immense.
All along the coast tens of thousands of homes and other buildings lie in ruins. Emergency crews are hard-pressed to reach all of them.
Reports from towns to the west of Gulfport say that local people have been moving bodies themselves from wreckage or from waterways.
Jamie Coomarasamy, New Orleans, Louisiana, 1206GMT
From a city on the edge of chaos, New Orleans is now coming to resemble a ghost town.
The massive deployment of the National Guard is having an effect, bringing a sense of order and speeding up the evacuation of the thousands still in the city.
The convention centre and the Superdome, scenes of lawlessness and the focus of much of the anger and frustration of recent days, have now been cleared.
The authorities still face the problem of reaching the areas worst affected by the flooding and of how to convince the people who have refused to leave, that it is in their best interest to do so.
Now that it has started in earnest though, the evacuation is proving to be swift and relatively efficient, throwing into even sharper focus how slow and inefficient it was initially.
Daniel Lak, Gulfport, Mississippi, 1102GMT
No one has been to some of the bayous and residential areas around this coast, no medical teams, no emergency services. It has got to be a priority very soon to get out there.
There is probably a third of the population or so still in this area, some of these have returned from higher ground.
This is still a total catastrophe here and people are feeling overshadowed by what's happening in New Orleans.
The security situation here is not on the scale of New Orleans with gangs and things but there have been incidents. A lot of expensive shops have been looted here.
People are trying to keep it to a minimum here and the national guard is deployed and there is a dusk until dawn curfew.
Andrew Bomford, Rosenburg, Texas, 1010GMT
You know it is going to be long term when visitors start enrolling their children at the local school and that has started to happen already. Across Texas 10,000 New Orleans children are expected to start new schools next week. This is a small town and the population here has doubled since last week.
Evacuees are being housed in shelters, churches, hotels and in peoples homes, they are enjoying a warm Texas welcome and that is putting a smile back on their faces.
I visited Lamar High School last night. At half time on the pitch the band was playing and I met some recent evacuees from New Orleans. One young man told me that there were 10 of his family members now living with another relative in this area. Another young woman told how her house is totally submerged in 20ft of water and she doesn't know if she will ever go back.
Justin Webb, Biloxi, Mississippi, 0920GMT
The latest from here is that the authorities have sorted themselves out and are now doing all the things they couldn't do in the first 24 hours. There are 17,000 more troops on their way and the refugees are now being taken to 19 different states.
Those desperate to get out are on their way, although some don't want to leave, but that's a different issue.
This administration is now flooding the place, President Bush is on his way south again for the second time. And the Secretary of State, Condoleezza Rice, who has nothing to do with this in relation to her professional capacity, is on her way too, and she is a black woman.
But there is a new troubled mood across the southern states of America where I have been travelling for the last few days.
As you drive round you have to wonder if the end of the world has arrived, not the whole world, but the lazy, hazy days of American empire.
Radios have gone mad, country music and the crazy preachers have been taken off the airways and panicked punch-drunk southerners have left the petrol stations dry.
Jon Sopel, Baton Rouge, Louisiana, 0811GMT
I think the extra resources are having an impact, thousands are being evacuated now, but there is still an awful long way to go.
Are people's lives suddenly going to be transformed, no - people are going to be taken to shelters where they are going to have an impatient and unhappy time.
It is not just the homes here that have blown away, it is business, companies - places of work - all gone. People are going to be without jobs and homes and that is going to be a testing time for them over the coming weeks.
Each day things are getting better but you still have to get all the agencies working together - getting them all on the same page. They are all doing fantastic work but co-ordination has been lacking in the first few days.
President Bush said no one should be dying because of bureaucracy but in the last few days that appears to be what has happened.
Michael Buchanan, Houston, Texas, 0632GMT
The State Department says there are no figures for the number of foreigners who are missing as a result of Hurricane Katrina but it's known that tens of thousands of people from Latin America for instance stayed in the New Orleans area including significant numbers of Hondurans and Mexicans.
So in an attempt to match the foreign nationals with their respective countries an international consulate centre has been opened beside the Houston astrodome where nineteen countries are ready to provide shelter and documentation for their citizens.
One fear the authorities have is that illegal immigrants who were caught up in the storm will refuse to come forward for help for fear of being deported.
In an effort to allay the concern of Mexicans the country's President Vicente Fox announced that he'd reached an agreement with US officials that any undocumented Mexicans in New Orleans at the time of the hurricane would not be persecuted.
Jamie Coomarasamy, New Orleans, Louisiana, 0449GMT
From a city on the edge of chaos New Orleans is now coming to resemble a ghost town. The massive deployment of the National Guard is having its effect bringing a sense of order and speeding up the evacuation of the thousands still inside the city.
The Convention Centre and the Superdome, scenes of lawlessness and the focus of much of the anger and frustration of recent days have now been cleared.
The American authorities still face the problem of reaching the areas worst affected by the flooding and of how to persuade the people who refuse to leave that it's in their best interest to do so.
Now that it's started in earnest though the evacuation is proving to be swift and relatively efficient throwing into even sharper focus just how slow and inefficient it was initially.
Daniel Lak, Gulfport, Mississippi, 0328GMT
America's largest insurances companies have put out radio advertisements and set up claims booths in several places along the coast.
Not all of the thousands of homes destroyed in the storm were properly insured and many homeowners could find themselves with no place to live yet still a mortgage to pay.
Businesses, especially construction companies are asking employees to return to work. The casinos destroyed in the wind and waves are issuing final pay cheques to their estimated fourteen thousand employees in the area and promising to re-open. Without gambling this coast would be much poorer.
But in the medium and long term it's likely that this already poverty-stricken part of the United States will see people migrating to other parts of the country or on welfare for the rest of their lives. Hurricane Katrina was a costly, as well as devastating storm.
Jamie Coomarasamy, New Orleans, Louisiana, 0005GMT
As you approach New Orleans the scene is a deceptive mixture of the ordinary and the extraordinary. On a casual glance at its skyline this appears to resemble any other American city with its skyscrapers and bridges apparently untouched.
But as you cross the Mississippi river and head into the centre of town you begin to notice the clouds of black smoke billowing from fires which are still burning across the city, and the silhouettes of military helicopters which are beginning to fill the sky.
For the past week, the roads leading into New Orleans have been virtually empty but now they are packed with convoys of emergency vehicles, many towing the small boats that will be essential to complete the evacuation and penetrate the flooded areas of the city where information remains murky.
Number plates from California to North Carolina reveal that this rescue operation has finally taken on the dimensions for which the people of this stricken city have been pleading. But it's taken five horrific days and a national sense of shame and horror for that to happen.