At least 78 people died in five US states in the center and south of the country Saturday due to tornadoes and storms, which President Joe Biden described as an "unimaginable tragedy."

Seventy deaths were counted in Kentucky alone, while three people died in Tennessee and two people in Arkansas, according to officials and local media.

Two people died in Illinois as a result of the collapse of an Amazon warehouse, while at least one death was recorded in Missouri.

"We were almost certain we were going to lose more than fifty (of the state's population)," Kentucky Governor Andy Beshear said in a press conference.

Pictures and videos spread on social media showed buildings destroyed by the storm, while twisted iron bars, uprooted trees and bricks littered the streets, leaving behind destroyed facades.

Many Kentucky counties were damaged by the most powerful tornado ever, and accompanying winds that exceeded 300 km.

The city of Mayfield, which has a population of 10,000, was considered the worst affected in the state.

A storm hit a large Amazon warehouse in Illinois, which housed nearly 100 employees, according to local media.

On Saturday, US President Joe Biden considered that tornadoes that left dozens of dead in the center of the United States constitute an "unimaginable tragedy."

Biden explained via Twitter that he was briefed on the latest developments on the ground, adding, "We are working with (state) governors to ensure that we have what is necessary for us to search for survivors."

The longest US hurricane ever tracked was a storm that spanned 219 miles in Missouri in 1925. It claimed 695 lives.

- 'The damage is unimaginable' -

Hundreds of officials made efforts throughout the night, until early Saturday, to rescue employees at the facility in Illinois, which has flattened a third of it. Staff were on the night shift to deliver orders before Christmas.

The Collinsville Emergency Management Agency feared "significant casualties" with "several people stranded in the Amazon warehouse".

"At first, we could hear the sound of rain. But all of a sudden, we heard a very loud thump like a train," Springs-based Dawson resident Laurie Wootton told CNN.

"I didn't think it would last long... He disappeared after three or four seconds. But when we got out of the house, the damage was unimaginable." So you have to be very careful."

Dean Patterson of the Kentucky Police Department noted that the damage "is unspeakable. The landscape of Mayfield as we know it is in a turbulent state," adding, "We've never seen what we're seeing now."

"My prayers are to the people of Edwardsville this night," Illinois Governor J.B. Pritzer said.

"The Illinois State Police and the Illinois Disaster Management Agency are 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 Rocca said, "The safety and well-being of our employees and partners is our highest priority now. We are studying the situation and will share additional information as it becomes available."

Craighead County Sheriff Marvin Day told local news channels that rescuers were able to get people trapped in the building, which was "severely damaged."

Scientists have warned that climate change is increasing the intensity and frequency of storms, which poses an increasing threat to regions already experiencing severe weather.