The five confirmed fatalities on Thursday were in Ohatchee, a town of about 1200 people in the northwestern corner of the state where a twister ripped apart homes and downed trees and power lines.

Calhoun County coroner Pat Brown confirmed to the Gadsden Times newspaper that three of those killed were family members in a house that was hit. In addition, an adult male died in his mobile home, and a female adult died in another mobile home.

No more fatalities were expected.

Rescue crews were tending to injured survivors and searching for additional victims, the agency said.

Photos posted on social media showed a line of buildings near Ohatchee that had collapsed or been ripped apart, with roofs sheared off, exposing furniture and other contents. A white church steeple, still intact, rested next to a destroyed structure.

Tens of thousands of people were left without power.

A police officer in Florence was struck by lightning as he set up road barriers, the police department there said. The officer was "conscious and responsive" at North Alabama Medical Center, Florence police said on Twitter.

At least two storms produced long tracking, violent tornadoes that swept across about 160km of Alabama on Thursday afternoon.

First lady Jill Biden cancelled a trip to Alabama with actress Jennifer Garner that had been planned for Friday to promote President Joe Biden's coronavirus relief plans, according to the White House.

Australian Associated Press