The number of people killed by a violent storm that triggered numerous powerful tornadoes across several south-central and eastern US states on Friday has surpassed 20, officials said late on Saturday.

Some 14 deaths were reported in Arkansas, Mississippi, Alabama, Indiana and Illinois, as well as another seven deaths in the state of Tennessee.

One of the worst hit areas was the state capital of Arkansas, Little Rock, where a powerful tornado passed through, leaving scattered debris in its wake.

The storm system also sparked wildfires in the southern plains and is expected to bring hail and blizzard conditions to the northeastern US, including parts of Pennsylvania and New York.

Experts said they will need days to determine the full extent of the storms and the exact number of tornadoes produced.

Widespread devastation

Arkansas Governor Sarah Huckabee Sanders declared a state of emergency and brought in the national guard to help with recovery. She also said that President Joe Biden had pledged expedited federal aid.

Several people were killed in collapsed buildings in Illinois, with tornadoes deemed the most likely culprit. Tornado warnings had also been declared in Mississippi where 25 people were killed by a twister last week.

Property damage across the large swathes of the US that were hit by the storms was also extensive. Over 610,000 homes had been left without power by Saturday, according to the poweroutage.us website.

Officials in Tennessee warned that Tuesday could see a repeat of the same weather conditions from Friday.

High wind warnings for several Mid-Atlantic states were in effect as the storm system moved northeast on Saturday afternoon.

"Maximum wind gusts could approach 60 miles (100 kilometers) per hour throughout much of the Appalachians, upper Ohio Valley and Mid-Atlantic today," the National Weather System warned.