Katrina kills hundreds

Helicopters plucked frantic survivors from rooftops of inundated homes yesterday and officials said hundreds of people may have died in Hurricane Katrina's attack on the US Gulf Coast, which sent a wall of water into Mississippi and flooded New Orleans.

The economic cost of the hurricane's rampage could be the highest in US history, according to damage estimates.

"The devastation is greater than our worst fears," Louisiana Governor Kathleen Blanco told a news conference. "It's totally overwhelming." She spoke after an overnight breach in New Orleans' protective levee system allowed water from Lake Pontchartrain to flood most of the city.

In the Mississippi coastal city of Biloxi, hundreds may have been killed after being trapped in their homes when a nine-metre storm surge came ashore, a city spokesman said.

"It's going to be in the hundreds," spokesman Vincent Creel said. "Camille was 200, and we're looking at a lot more than that," he said, referring to Hurricane Camille, which hit the area in 1969 and destroyed swaths of Mississippi and Louisiana, killing a total of 256 people.

New Orleans Mayor Ray Nagin reported bodies floating in the city's floodwaters. Rescuers struggled through high water and mountains of debris to reach areas devastated by Katrina when it struck the Gulf Coast region on Monday. The storm inflicted catastrophic damage all along the coast as it slammed into Louisiana with 224 kph winds, then swept across Mississippi, Alabama and Tennessee.

It shattered buildings, broke boats, smashed cars, toppled trees and flooded cities. Risk analysts estimated the storm would cost insurers $26 billion, making Katrina potentially the costliest US natural disaster. Most of the deaths appear to have been caused by the storm surge, which swept as far as 1.5 kilometres inland in parts of Mississippi. Hundreds of people climbed onto rooftops to escape the rising water and waited to be rescued. Others may have been trapped in attics.

In New Orleans, "We probably have 80 per cent of our city under water; with some sections of our city the water is as deep as six metres," Mr Nagin told television station WWL. "Both airports are under water." New Orleans is a bowl-like city mostly below sea level and protected by levees or embankments. The levees gave way overnight in places, including a 60-metre breach that allowed the lake waters to pour into the city centre.

Pumps failed and floodwaters threatened downtown and the historic French Quarter.

"We always were afraid the bowl that is New Orleans would fill quickly," Walter Maestri, emergency management coordinator for Jefferson Parish, said in a radio interview. "Now with the water rising today, it appears to be filling slowly."

Tulane University Medical Centre Vice President Karen Troyer-Caraway told CNN the downtown hospital was surrounded by two metres of water and considering evacuating its 1,000 patients.