At least 14 people were killed overnight in Kentucky in the wake of severe storms, and the death toll is expected to rise, Gov. Andy Beshear said on Saturday, after the dangerous weather system ripped across the state and neighbouring Missouri, spawning tornadoes.

Earlier, NBC News reported that at least 16 people were killed as the severe weather swept through parts of the two states.

It was not immediately clear whether the deaths announced by Beshear in a post on social media platform X were included in the total cited in the NBC report.

Beshear also declared a state of emergency for his state in the wake of the storm system, which levelled mobile homes in the city of Morganfield, Ky., according to broadcaster WLKY in Louisville.

Earlier, officials said a tornado ripped through the Missouri city of St. Louis, damaging 5,000 properties as it tore off roofs. It also knocked down power lines and swept through a major thoroughfare during rush-hour traffic on Friday, officials said.

Five people were killed in St. Louis, and two others in Scott County, in southeastern Missouri, according to officials, the NBC report said.

"Our city is grieving tonight," St. Louis Mayor Cara Spencer, who was sworn in a month ago, told reporters on Friday night.

"The loss of life and the destruction is truly, truly horrendous."

A spokesperson for both St. Louis Children's Hospital and Barnes-Jewish Hospital told NBC news that at least 35 people had been admitted to the facilities, with the children's facility receiving 15 and Barnes-Jewish taking in at least 20 — possibly 30 — people who were injured as a result of the severe weather.

The city imposed a curfew from 9 p.m. to 6 a.m. local time in two police districts where most of the damage took place, to prevent injuries from dangerous debris and reduce the potential for looting.

At the time of the deadly twister, a hazardous weather advisory was in effect for eastern Missouri, including the St. Louis area, warning of severe thunderstorms through early Friday evening, and a tornado watch was posted for areas immediately to the southeast.

The National Weather Service said thunderstorms were widespread across portions of the Mississippi, Tennessee and Ohio valleys on Friday, along with the potential for heavy rains and flash flooding.

About 500 first responders, including 17 search teams, were deployed, and early indications suggested the number of injured was relatively small considering the overall damage, fire Chief Dennis Jenkerson said.

The National Weather Service reported at least half a dozen tornadoes touching down in Missouri and neighbouring Illinois, and other severe weather stretching all the way to the Atlantic coast, including another tornado in New Jersey.