Kentucky governor Andy Beshear said on X that at least 14 people had died in the storms Friday night, while local officials in Missouri said another seven were dead there.

Jamie Burns, 38, who lives with her husband and son in a trailer home in the town of London, Kentucky, had to seek shelter in the basement of her sister's brick house while the storm destroyed some 100 to 200 houses in the area.

"Things that have been here longer than I have, things that have been here for 30-plus years are just flat," Burns told AFP in a phone interview, her voice quavering.

"It's wild, because you'll look at one area and it's just smashed... totally flattened, like, not there anymore."

Drone footage published by local media showed scenes of devastation in London, with houses leveled and reduced to splinters and tree trunks standing bare, completely shorn of branches.

Beshear added that more than 100,000 people have been left without power in the state, and five counties have declared a state of emergency.

Eastern Kentucky, an area historically known for its coal mines, is one of the poorest regions in the country. "A lot of us live in manufactured homes that aren't safe for tornado weather," said Burns.

- 'Our city is grieving' -

In Missouri, five people were killed in the large city of St. Louis and two in Scott County, the State Highway Patrol said in a statement to AFP.

More than 80,000 people were left without power and three shelters were opened in the area, the statement added. More severe weather was forecast for Sunday night and Monday.

"Our city is grieving tonight," St. Louis mayor Cara Spencer told reporters Friday night. "The loss of life and the destruction is truly horrendous."

Derrick Perkins, a pastor at the Centennial Christian Church in St. Louis, said the city was devastated by tornadoes, which are spinning columns of air that touch the ground from massive cumulonimbus thunderstorm clouds.

"It's horrific for a tornado to come through here and cause this much damage to the residents and also to the church," Perkins told CBS. "Our hearts are broken."

Bruce Madison, who also works at the church, said the community was coming together in the face of the tragedy.

"Right now, we're just praying for... everybody that they're trying to find right now."

While there were warnings ahead of the severe weather -- Beshear had protectively declared a state of emergency Friday -- the latest outburst may raise questions about whether sharp cuts by the Trump administration have left National Weather Service forecasting teams dangerously understaffed, forcing some offices to curtail operations.

An estimated 500 of the 4,200 NWS employees have been fired or taken early retirements this year, according to the Washington Post.

The United States saw the second-highest number of tornadoes on record last year with nearly 1,800, according to the National Oceanic and Atmospheric Administration (NOAA), trailing only 2004.