'Biloxi's tsunami': building collapse kills 30

"The devastation is just enormous," Haley Barbour said. "We know that there is a lot of the coast that we have not been able to get to. It looks like it is a very bad disaster in terms of human life."

As rescuers in boats and helicopters searched for survivors stranded by flood waters, it became increasingly clear that the communities of Mississippi's Gulf Coast - struck by a 25ft storm surge - had borne the worst of the weather. More than 1,600 Mississippi National Guardsmen were mobilised and the Alabama Guard said it was sending two battalions, but fallen tree trunks and power lines and debris littering streets were hampering efforts to rescue people.

Biloxi's mayor, A J Holloway, said: "This is our tsunami. Highway 90 is destroyed. I saw a disaster. Water did not get this high for Camille [the deadly hurricane that struck the area in 1969]." Governor Barbour said that up to 80 people may have been killed in Harrison County.

Officials said that many people were killed on Point Cadet, at the south-eastern tip of Biloxi's peninsula. Some bodies may have been washed away, never to be found. Assistant police chief Rodney McGilvary said: "We'll be trying to determine a total fatality count, if we ever have one."

Emergency medical personnel were struggling to deal with the number of people needing help.Christopher Cirillo, Harrison County emergency medical services director, said staff had seen many people suffering from cuts, broken bones, electrocution from downed power lines and breathing difficulties from the stifling heat.

Officials said tens of thousands of people may be unable to return for several months. Patrick Rhode, deputy director of the Federal Emergency Management Agency, said it could take until the end of September to restore power. "We do need to tell people to get used to where you are at the moment because this may not end for some time," he said.