Some 77 people have died in severe storms ripping through the southern United States, global media said on Thursday, according to RIA Novosti.
Alabama State has been the worst affected, with 61 people recorded dead. A huge tornado ripped through the city of Tuscaloosa, badly damaging The University of Alabama and crippling the city`s infrastructure.
A nuclear power plant west of Huntsville lost power and was forced to operate on diesel generators.
U.S. President Barack Obama has approved emergency aid for the state.
"While we may not know the extent of the damage for days, we will continue to monitor these severe storms across the country and stand ready to continue to help the people of Alabama and all citizens affected by these storms," Mr Obama said in a statement on Wednesday night.
Governors in Alabama, Arkansas and Tennessee declared states of emergency following a fresh round of heavy winds, rain and tornadoes.
More than 50 tornados were recorded in the region on Tuesday.
The storms are forcast to hit the Carolinas next before moving north east. The National Weather Service says the storms may affect 21 states from the Great Lakes to the Gulf of Mexico.