At least 19 people died as tornadoes ripped through Tennessee early Tuesday, destroying buildings and toppling power lines hours before the southern US state was to vote in Super Tuesday primaries, officials said.
Devastation could be seen across the rubble-strewn state capital Nashville, where a tornado touched down shortly after midnight.
Residents described running for their lives as their homes came down around them, with the authorities reporting that tens of thousands of residents were without power.
"TAKE COVER NOW! THIS IS AN EXTREMELY DANGEROUS STORM!!!" the National Weather Service tweeted as one twister tore through an area west of Nashville.
Footage broadcast by the local ABC affiliate showed cars piled up, hangars destroyed and what appeared to be dozens of aircraft smashed into each other at Nashville's John C. Tune airport.
"In the hours ahead, we will continue deploying search and rescue teams, opening shelters across the state, and sending emergency personnel to our communities hit hardest," Governor Bill Lee wrote on Twitter.
Tennessee Emergency Management Agency (TEMA) public information officer Maggie Hannan confirmed to AFP that the toll had climbed to 19 across four counties.
The Nashville Fire Department tweeted that it was responding to reports of approximately 40 structure collapses around the city, while overturned tractor trailers and other vehicles littered state highways.
US President Donald Trump tweeted that "we will continue to monitor the developments. The Federal Government is with you all of the way during this difficult time."
The series of severe storms that passed through Tennessee caused major damage "to buildings, roads, bridges, utilities and businesses in several counties," TEMA said.
"Tornado damage has been reported throughout West and Middle Tennessee including downtown Nashville," it added.
- 'The house just exploded -
In the city's East Nashville neighborhood, resident David Haskell said that he and his wife bolted into their storm shelter after an alarm on their phone went off.
"Ten seconds later the house just exploded," he told the local Tennessean newspaper, standing in front of his home, with its crumbled walls and destroyed roof.
Mayor John Cooper wrote on Twitter that "Nashville is hurting, and our community has been devastated," as he urged people to lend a helping hand.
More than 47,000 customers were without power, Nashville Electric reported.
Tennessee is one of 14 states voting in the crucial Super Tuesday primaries, which will help determine the Democratic nominee for November's presidential election.
Cooper told a news conference that 15 polling stations had been affected by storm damage, which was less than 10 percent of the total.
Voting was to start an hour late in Nashville and Wilson County due to the tornado damage, according to The Tennessean.
The Democratic candidates vying to take on Trump in November's election were quick to acknowledge the tragedy as Tennesseans headed to the polls.
"We have been watching the news coming out of Tennessee with heavy hearts," former New York mayor Mike Bloomberg tweeted.
Massachusetts Senator Elizabeth Warren meanwhile said she was "heartsick for the victims and their families."
Actress Reese Witherspoon, who grew up in Nashville, meanwhile stated: "I'm just heartbroken and saying special prayers for the families who lost loved ones."
Nashville is best known as the epicenter of the US country music scene.