In the deadliest series of tornadoes in nearly four decades in the United States, 131 people were killed in Alabama, the worst-hit state which suffered "massive destruction of property," Governor Robert Bentley said on Thursday.
"We expect that number to rise."
He added that six million people were still without power.The clusters of powerful tornadoes - more than 160 in total - combined with storms to cut a swathe of destruction heading from west to east over several days.
In preliminary estimates, other state officials reported 32 killed in Mississippi, 30 in Tennessee, 11 in Arkansas, 14 in Georgia, eight in Virginia and two in Louisiana.
Some of the worst devastation occurred on Wednesday in Alabama, where a massive 1.6 km tornado slammed into the town of Tuscaloosa, town of around 95,000 in the west-central part, killing at least 37 people including some students.
"It sounded like a chain-saw. You could hear the debris hitting things. All I have left is a few clothes and tools that were too heavy for the storm to pick up. It doesn't seem real," Steve Niven, a local resident, told Reuters news agency.