Up to 100 people are feared dead in Kentucky after the “deadliest tornado storm ever” unleashed catastrophic damage in several US states.

Four tornados ripped through the state, with the largest on the ground for more than 227 miles (365km).

People are feared dead in 10 counties, with the city of Mayfield left devastated by the severe weather system.

Thousands have been left without power – with many residents forced to flee with a handful of belongings.

“Everywhere along the line of this tornado that touched down and stayed down for over for 227 miles has been severely and significantly impacted,” said Governor Andy Beshear, who has declared a state of emergency.

“It’s been one of the toughest night’s in Kentucky’s history,” he said, adding: “The damage is even worse now that we have first light.”

Rescue efforts in Mayfield were hampered by hurricanes sweeping through the city’s main fire station and emergency services (EMS) hub.

Fire chief and EMS director, Jeremy Creason, told how crews had been working “tirelessly through the night” adding: “We had to at times crawl over casualties to get to live victims to get them out.”

At least six people are believed to have died in other states – including one at an Amazon warehouse in Illinois where a wall the length of a football field collapsed, together with the roof.

Around 100 workers are believed to have been working the night shift at the time.

The storms also hit a candle factory in Mayfield, with 110 people feared to be inside.

One person died and several were injured after the deadly weather struck a nursing home in Arkansas.

President Joe Biden tweeted that he was briefed on the “devastating tornadoes” across the central US on Saturday morning.

He wrote: “To lose a loved one in a storm like this is an unimaginable tragedy.”

The White House is working with state governors to ensure they have the necessary resources as the search for survivors continues.