At least 50 dead in Kentucky as storms batter US

At least 50 people are dead after four tornadoes tore through the southeastern US state of Kentucky, its governor told reporters early Saturday, as several storms ravaged swathes of the country.

A number of counties in Kentucky were left devastated with the strongest tornado tearing through 200 miles of the state, Governor Andy Beshear said.

On the same night a storm ripped through a massive Amazon warehouse in the state of Illinois where around 100 workers were left trapped inside, local media reported.

"I fear that there are more than 50 dead ... probably closer to somewhere between 70 and 100, it's devastating," Beshear said, adding that it was the "most severe tornado event in Kentucky's history."

In one incident, the roof of a candle factory collapsed, resulting in "mass casualties" in the city of Mayfield, the governor added.

Pictures and videos shared on social media from Mayfield showed buildings ripped apart by the storm, with bent metal, trees and dislodged bricks scattered across the streets and only the remnants of houses left behind.

Images of the tornadoes from US news channels showed a black cylinder sweeping across the ground, illuminated by intermittent blasts of lightning.

"Before midnight I declared a state of emergency," Beshear said.

He added that scores of search and rescue officials had been deployed to save lives as power outages continued to hit the area.

'Prayers'

The tornado came as storms wreaked havoc in multiple US states.

Hundreds of officials were working through the early hours of Saturday to rescue employees at an Amazon warehouse — a third of which was reduced to rubble — who were on the night shift processing orders ahead of the Christmas holidays.

The Collinsville Emergency Management Agency described it as a "mass casualty incident" with "multiple subjects trapped at Amazon Warehouse."

A tornado warning had been in effect in the area at the time.

Footage shared across US news channels and social media of the Amazon warehouse in the city of Edwardsville showed a large part of the facility's roof ripped off, while one of the walls had collapsed into the building, with rubble strewn across the site.

Edwardsville police said in a statement there were "confirmed fatalities".

Illinois Governor J.B. Pritzker said: "My prayers are with the people of Edwardsville tonight."

"Our Illinois State Police and Illinois Emergency Management Agency are both coordinating closely with local officials and I will continue to monitor the situation," he added.

In a statement sent to local media, Amazon spokesperson Richard Rocha said "the safety and well-being of our employees and partners is our top priority right now. We're assessing the situation and will share additional information when it's available."

In Arkansas, one person was killed and 20 others were trapped after a tornado struck the Monette Manor nursing home, US media reported, with another person killed elsewhere in the state.

Craighead county official Marvin Day told local news channels that rescuers had successfully pulled out those trapped in the building and the structure was "pretty much destroyed".

In Tennessee, at least two people were killed in storm-related incidents, an emergency management official told local media.

The tornadoes tore through the four states — Missouri, Arkansas, Kentucky and Tennessee — with warnings in effect for Illinois.

Scientists have warned that climate change is making storms more powerful and increasing their frequency, posing a growing threat to areas where extreme weather events are already common.