A sheriff's deputy drives down a street without houses that were destroyed by a tornado in Phil Campbell, Alabama, April 30, 2011. [Photo/Agencies]

* Survivors in shelters, camped out in shattered homes

* Property insurance losses estimated at $2 billion to $5 billion

PLEASANT GROVE, Alabama - The death toll from the second deadliest US tornado outbreak on record rose above 350 on Saturday as thousands of stunned survivors camped out in the shattered shells of their homes or moved into shelters or with friends.

With some estimates putting the number of homes and buildings destroyed close to 10,000, state and federal authorities in the US South were still coming to terms with the scale of the devastation from the country's worst natural catastrophe since Hurricane Katrina in 2005.

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One disaster risk modeler, EQECAT, is forecasting insured property losses of between $2 billion and $5 billion from the havoc inflicted by the swarm of violent twisters that gouged through seven southern states this week.

The death toll in Alabama, the hardest-hit state, rose to 255 on Saturday, with at least 101 more deaths reported in Mississippi, Tennessee, Arkansas, Georgia, Virginia and Louisiana.

"We're in the thousands of homes completely gone ... It's not an exaggeration to say that whole communities were wiped out," Yasamie August, spokeswoman for the Alabama Emergency Management Agency, told Reuters.

In many communities in the US South, the scenes of destruction with tangled piles of rubble, timber, vehicles and personal possessions recalled the devastation seen in the recent Japanese earthquake and tsunami.

Power and water were still out in many areas.

"It is like living in some other world. Devastation is everywhere," said Pastor John Gates of the United Methodist Church in Pleasant Grove, a community with a population of some 10,000 west of Birmingham, Alabama.

The death toll from the week's tornado outbreak, which is still expected to rise, was the second highest inflicted by this kind of weather phenomenon in US history. In March 1925, 747 people were killed after tornadoes hit the US Midwestern states of Missouri, Illinois and Indiana.

President Obama, mindful of criticism that President George W. Bush was too slow to respond to the 2005 Katrina catastrophe, visited the wrecked city of Tuscaloosa, Alabama, on Friday to pledge full federal assistance for the states hit.

Some of the twisters - the winds of one in Smithville, Mississippi, was recorded reaching 205 miles (328 km) per hour - picked up people and cars and hurled them through the air.

Rescuers were still searching for bodies and those unaccounted for. But the total of missing was not clear.

A combination of images from GeoEye's IKONOS high-resolution satellite shows an overview of the path of destruction after a massive tornado touched down in Pleasant Grove area in Birmingham, Alabama, April 28, 2011 (L) and an image taken May 13, 2001. [Photo/Agencies]

Many whose homes only lost roofs and windows were camping inside with tarps and plastic sheeting over them, but those whose houses were completely razed were forced to move in with family or friends or go into government shelters.

"Most people are living in the parts of their houses that are still standing. But for some people, you can't even tell where their houses were. They are with family, friends or in hotels," said Gates, 63.

"We still have missing people to find," he added.

There were 659 people in shelters across Alabama, August said. Tennessee had 233 people in shelters.

As state and federal authorities increased efforts to clear rubble and provide food and water to homeless survivors, volunteers in many local communities also turned out to help the most affected.

"There's lots of commotion with big trucks coming in and the sound of chainsaws. Big grills are set up everywhere to offer people food. The community has really pulled together, said Tammy Straate, 29, a foster mother in Pleasant Grove who cares for 11 children ages 5-16.