At least 19 people were killed when a tornado and severe storms swept through the US state of Mississippi late Friday, authorities told ABC News.

Search and rescue operations were underway in Sharkey and Humphreys counties, about 70 miles (110 kilometers) north of state capital Jackson, the Mississippi Emergency Management Agency (MEMA) said, according to ABC.

"Many in the (Mississippi) Delta need your prayer and God's protection tonight," Governor Tate Reeves said on Twitter.

"We have activated medical support -- surging more ambulances and other emergency assets for those affected. Search and rescue is active," he added, warning residents to "watch weather reports and stay cautious."

ABC reported that 13 people had died in Sharkey County, three in nearby Carroll County and another two in Monroe County.

In Humphreys County's Silver City, a state highway patrol trooper told ABC that one person had died.

TV footage showed homes leveled and debris strewn across roads as emergency services attempted to get to those who needed help.

"As far as official damage numbers, we're not going to have that until morning, daylight time," said MEMA's Malary White.

"Our main priority right now, especially for the local first responders, it's life safety and accounting for the people and making sure they are safe," she told CBS News affiliate WJTV.

Tornado warnings had been issued in various counties throughout the state on Friday, but by 2:48 am local time (0748 GMT) on Saturday, the National Weather Service for Jackson said the "tornado watch has expired across our forecast area".

"Additional showers and thunderstorms are expected across our area," it said on Twitter, adding that they were "not expected to become severe."