Tornadoes and thunderstorms, termed catastrophic by U.S. President Barack Obama, that swept across the southern United States the past few days, left a trail of death and destruction - properties worth millions of dollars were damaged, nearly 300 people are dead and hundreds of thousands injured.

The tornadoes, deemed as the country's deadliest in almost four decades, has devastated the southern state of Alabama, prompting Governor Robert Bentley to sound high alert. At least 195 people in Alabama, which is one of the eight states to be hit by the storm, have died. Alabama's city of Tuscaloosa was one of the hardest hit. Meteorologists said the tornado that hit Tuscaloosa could have been on the ground for 176 miles, with winds between 167 and 200 mph. Tuscaloosa, a bustling city, looked like a ghost town with rubble all around.

Bentley has deployed 2,000 National Guard troops to assist in the search-and-rescue efforts. There is some massive devastation out there, he said.

Obama said the death toll is heart-breaking and has promised that the federal government will do everything it can to help the region recover. In a matter of hours these deadly tornadoes...took mothers and fathers, sons and daughters, friends and neighbors, even entire communities, the president said.

The national weather service has estimated that about 150 tornadoes tore through parts of Mississippi and Alabama alone, flattening buildings and causing power outage. Other states to be badly shaken are Georgia, Tennessee, Virginia and Arkansas.

Meanwhile, concerns are growing about the condition of the Browns Ferry nuclear power plant in northern Alabama. Bentley said the plant's safety systems are working, dismissing fears of radiation leak.

See below a video of the destruction left behind by the 'perfect storm.'