Storms and tornadoes killed at least six people and left dozens injured when they ripped through large swathes of the eastern United States on Wednesday, reports and officials said.

Homes were badly damaged or even leveled and at least two people were missing as a series of tornadoes and twisters tore rapidly through several states, leaving a trail of destruction.

But the danger was not over, with more strong tornadoes threatening parts of Tennessee, Alabama, Kentucky and Mississippi and severe thunderstorms also stalking the region, the National Weather Service said, issuing dozens of weather warnings.

Initial reports said the youngest victim was a boy aged seven who was found dead as a result of a storm in Mississippi, ABC and NBC News said.

Reports said the storm picked up and tossed the car he was traveling in.

At least 40 people were injured in the state, the Mississippi Emergency Management Agency said.

Nearly 70 million people were forecast to be in the path of the storms Wednesday night, ABC said, with the number of dead and injured expected to rise.