Tornadoes have killed at least 19 people and destroyed dozens of buildings in the US state of Tennessee - including causing severe damage in downtown Nashville.

The twisters toppled power lines and trees and ripped off roofs, causing gridlock on the streets of the famous musical city.

Police and fire crews were dealing with about 40 building collapses, said Metro Nashville police.

Severe storms were also whipped up by the tornadoes as they moved across the southeastern US state after midnight.

"A tornado skipped across the county," said Nashville Mayor John Cooper on a visit to an emergency shelter.

"You do have people at the hospital and frankly there have been fatalities."

A video posted online from east Nashville appeared to showed the tornado moving quickly across the city accompanied by lightning.

The scene at Donelson Christian Academy after a tornado touched down in Nashville, Tennessee | Image: USA TODAY Network/SIPA USA/PA Images

One tornado reportedly stayed on the ground into Hermitage, 16km east of Nashville, with buildings, bridge and roads damaged.

"Our community has been impacted significantly," the Mount Juliet Police Department tweeted.

"We continue to search for injured. Stay home if you can."

Country singer Carrie Underwood was one of those affected and said her husband and children had to shelter in their safe room as the tornado hit.

Hangars were destroyed at Nashville's John C Tune Airport, with a spokesman saying it had "sustained significant damage".

Schools, courts and rail lines were also closed - and some polling stations were damaged just hours before crucial Super Tuesday voting.

Dozens of people in the city were seen carrying their belongings through the streets after the tornado barrelled through the city.

The local Red Cross has opened a shelter for people made homeless.

Nashville Electric said 44,000 people had lost power after four substations were damaged.