Martial law was declared in parts of New Orleans today after America's deadliest hurricane in more than 30 years caused a storm surge that breached the historic city's flood defences and left most of it under water.
More than 80 people are thought to have been killed by Hurricane Katrina, which rushed across Mississippi, Louisiana and Alabama yesterday and there are fears that the death toll could reach triple figures as emergency teams reach remote areas on the Gulf Coast
The flood levees protecting New Orleans, which lies below sea level, were breached in at least two places overnight and waters up to 6m (20ft) high are running through the streets, bringing destruction that the city thought it had been spared when the eye of the hurricane swerved past yesterday morning.
Looters in New Orleans took full opportunity of the chaos, emptying shops and pharmacies, sometimes in full view of police and troops.
"The city of New Orleans is in a state of devastation. We probably have 80 per cent of our city under water, with some sections of our city the water is as deep as 20ft. We still have many of our residents on roofs," said Mayor Ray Nagin. "Both airports are under water."
Kathleen Blanco, the Lousiana Governor, said that no reliable death toll from the city was available, but "many lives have been lost".
She added: "The devastation is greater than our worst fears. It is just totally overwhelming. We need to save as many people as we can save, and that is our mission for today...It is a tragedy of great proportions."
Residents who fled the city at the weekend were told that most of the city would remain uninhabitable for days, if not weeks. Some 10,000 people took refuge last night at the New Orleans Superdome, which was itself badly damaged in the storm.
Storm surges have reportedly sent the waters of Lake Pontchartrain, which hangs over New Orleans, rushing into the city through two gaps in the levee, one two blocks long. The flood has polluted the city's drinking supply and caused one hospital to consider evacuating its patients by helicopter.
Karen Troyer-Caraway, the vice president of Tulane University Medical Centre told CNN that the downtown hospital was surrounded by 6ft of water and preparing to move its 1,000 patients.
"The water is rising so fast I cannot begin to describe how quickly it’s rising," she said. "We have whitecaps on Canal Street, the water is moving so fast."
Across the city, the sudden, rising waters have forced people to take refuge in attics, with reports of families having to cut themselves free with axes and even blasting their way through roofs with shotguns.
Dozens of looters were reportedly arrested and residents of two areas - Jefferson Parish and Plaquemines Parish - were told to keep off the streets after martial law was imposed.
Elsewhere, communities across the Gulf Coast were searching for survivors and assessing the damage caused by the greatest storm to hit the region since Hurricane Camille in 1969. The deadliest storm to hit America in recent decades was Hurricane Agnes, which killed 122 people in 1972.
This morning, Haley Barbour, the Governor of Mississippi, the worst-hit state, said that there were unconfirmed reports of 80 deaths in one county alone.
"The devastation down there is just enormous," Mr Barbour said of Harrison County, a coastal strip of resorts and casinos flattened by Katrina's 145mph winds when the storm ran ashore yesterday morning.
"We know that there is a lot of the coast that we have not been able to get to," Governor Barbour told NBC television. "I hate to say it, but it looks like it is a very bad disaster in terms of human life."
Two towns in Harrison County, Biloxi and Gulfport, took the brunt of the hurricane. At least 50 people are believed to have been killed in Biloxi, of whom 30 died when a beachfront apartment complex collapsed under the weight of the winds.
Three other people were killed by falling trees in Mississippi and two died in a traffic accident in Alabama, authorities said.
"This is our tsunami," A.J Holloway, the local mayor, told the Biloxi Sun Herald newspaper.
Other local reports described families looking for their houses and casinos tipped over on the sand. Thousands of trees have been uprooted and sailboats have been thrown across motorways. The death toll from Katrina - which also killed 11 people as it hit the Florida Panhandle last week - is expected to rise.
The Gulfport fire chief, Pat Sullivan, said: "Let me tell you something, folks: I’ve been out there. It’s complete devastation."
More than a million homes remain without electricity as the rescue operation and search for more victims continues today. Power companies have warned that it will take weeks to return electricity across the region.
From on board Air Force One, President Bush declared major disasters in Mississippi and Louisiana, ordering military search and rescue experts to the Gulf Coast, along with water, power generators and baby formula.
"Our Gulf Coast is getting hit and hit hard," said Mr Bush, who will return to Washington from his holiday in Texas two days earlier than scheduled.
Insurance estimates today said Hurricane Katrina had caused up to $16 billion (£9 billion) of damage, less than was forecast when the main force of the storm was heading for downtown New Orleans. Damage to oil refineries in the Gulf region appeared to be less than expected.
This morning, Katrina was downgraded to a tropical storm as it passed through eastern Mississippi, moving north at 21mph. Forecasters say the hurricane could trigger tornadoes and heavy rain as it moves inland.
In New Orleans, audacious looters Orleans ransacked shops in the city, with some floating rubbish bins filled with clothing and jewellery down streets.
At a Walgreen’s pharmacy in the French Quarter, people were running out with baskets and boxes full of soft drinks, crisps and nappies. When police finally arrived, a young boy stood in the door screaming, "86! 86!", the radio code for police, and the crowd scattered.
Denise Bollinger, a tourist from Philadelphia, stood outside and snapped pictures in amazement. "It’s downtown Baghdad," the housewife said. "It’s insane. I’ve wanted to come here for 10 years. I thought this was a sophisticated city. I guess not."
At another pharmacy on Canal Street, two police officers with pump shotguns stood guard as workers from the Ritz-Carlton Hotel across the street loaded large laundry bins full of medications, snack foods and bottled water. "This is for the sick," Officer Jeff Jacob said. "We can commandeer whatever we see fit, whatever is necessary to maintain law."
Another office, D.J. Butler, told the crowd standing round that they would be out of the way as soon as they got the necessities. "I’m not saying you’re welcome to it," the officer said. "This is the situation we’re in. We have to make the best of it."
