Overwhelmed authorities struggled to rescue the living and count the dead today amid catastrophic destruction left in the path of powerful Hurricane Katrina.
The Mayor of New Orleans said the hurricane probably killed thousands of people in the city. "We know there is a significant number of dead bodies in the water," and others dead in attics, Mayor Ray Nagin said.
Asked how many, he said: "Minimum, hundreds. Most likely, thousands."
The US Energy Department said it would release oil from the country's strategic reserve to offset losses in the Gulf of Mexico, where the storm had shut down production and driven prices higher.
The storm killed at least 100 people in Mississippi, officials confirmed. They said the death toll was almost certain to go much higher.
"We're just estimating, but the number could go double or triple from what we're talking about now," a civil defence director told the Jackson, Mississippi, Clarion Ledger. Biloxi, Mississippi, spokesman Vincent Creel earlier said of the death toll, "It's going to be in the hundreds."
Governor Kathleen Blanco said the situation was desperate and there was no choice but to clear out. "The logistical problems are impossible and we have to evacuate people in shelters," the governor said.
"It's becoming untenable. There's no power. It's getting more difficult to get food and water supplies in, just basic essentials."
Senator Mary Landrieu told reporters she had heard at least 50 to 100 people were dead in New Orleans, where rescue teams were so busy saving people stranded in flooded homes they left bodies floating in the high waters.
Louisiana officials said 3,000 people had been rescued, but many more waited to be picked up by rescuers in boats which cruised up and down flooded streets or helicopters buzzing overhead.
Wild scenes of looting erupted around the city as people broke into shops to grab supplies, but also television sets, jewelry, clothes and computers. "It's a lot of chaos right now," Louisiana state police director HL Whitehorn said.
Katrina struck Louisiana on Monday with 224 kph winds, while slamming into the coasts of neighboring Mississippi, Alabama and western Florida. A 10-metre storm surge in Mississippi wiped away 90 per cent of the buildings along the coast at Biloxi and Gulfport, leaving a scene of destruction that Mississippi Governor Haley Barbour compared to a nuclear detonation.
New Orleans at first appeared to have received a glancing blow from the storm, but the raging waters of Lake Pontchartrain tore holes in the levee system that protects the low-lying city, then slowly filled it up.
Mayor Ray Nagin said 80 per cent of the city, much of it below sea level, was covered with water that was in places 6 metres deep. Attempts yesterday to plug a 60-metre gap with sandbags and concrete barriers in the levee failed, but officials said they would try again today.
The lake, whipped high by the storm, should return to normal levels within about 36 hours and the water now flooding New Orleans would begin to drain, said US Army Corps of Engineers senior project engineer Al Naomi.
He said the historic French Quarter, the main draw for New Orleans' huge tourist industry, should escape with only minor flooding because it sits 1.5 metres above sea level. The floods knocked out electricity, contaminated the city water supply and cut off most highway routes into New Orleans.
In Jefferson Parish, one of the hardest-hit areas, parish president Aaron Broussard said a complete rebuilding would be required. "Jefferson Parish as we knew it is gone forever," he told reporters.
A million people fled the New Orleans area before Katrina arrived, but those who stayed were running out of food and water. Amid the looting, gun-toting citizens took to the streets in some areas to try to restore order.
Mayor Nagin said 3,500 National Guard troops were being sent to the city.
Before striking the Gulf Coast, Katrina last week hit southern Florida and killed seven people. It knocked out electricity to about 2.3 million customers, or nearly 5 million people, in Louisiana, Mississippi, Alabama and Florida, utility companies said. Restoring power could take weeks, they warned.
US Energy Secretary Samuel Bodman said oil from the Strategic Petroleum Reserve could be provided to an unnamed oil refining company as early as Thursday. "This is not just a problem for the Gulf coast, this is a problem for America," he said on CNN.
Looters ran wild in New Orleans, while officials tried to plug a leaking levee that was allowing lake water to pour into the city.