NEW ORLEANS, United States (AFP) - Helicopters plucked victims from roofs and rescuers dodged submerged live power lines and spewing gas pipes as still rising floodwaters turned New Orleans into a disaster zone.
Local television reported that as conditions worsened, martial law was imposed in two areas, Jefferson Parish and Plaquemines Parish, a day after murderous Hurricane Katrina slammed into the city.
Police were halting anyone trying to get into the city, WWL-TV said.
Authorities said New Orleans, with highways submerged, bridges washed out and even elevated expressways unsafe, was effectively cut off, and waters were devouring more and more real estate after a storm surge breached a levee.
WWL-TV reported, quoting unidentified local officials, that flood waters were still coursing into the city, and were beginning to threaten areas in the historic French Quarter and downtown which were on higher ground.
Another local station, WDSU, warned viewers that the Louisiana Superdome, which welcomed at least 10,000 evacuees on Monday, was now surrounded by three feet (one metre) of water.
Evacuees sat tight in the massive sports arena, which itself bore Katrina's scars after having much of its outer dome ripped off.
Communications with New Orleans were largely cut off and around 700,000 people were without power. Some victims had been stuck on the roofs of their homes for nearly 24 hours in a spiralling humanitarian crisis.
Water was unsafe to drink in many areas, if available at all, as the Red Cross swung a massive relief operation into action to aid a city metropolitan area population of 1.4 million.
"Our city is in a state of devastation," Mayor Ray Nagin told WWL-TV "we probably have 80 percent of our city under water."
"With some sections of our city, the water is as deep as 20 feet" (seven metres).
With live power lines, gas pipes and debris including submerged cars floating below the surface of foul waters, it was too dangerous for rescue workers to use boats in some areas, meaning helicopters were the only choice.