A fierce tornado has blasted through Little Rock, Arkansas, and neighbouring towns, killing at least two people and injuring dozens of others as it sheared roofs and walls from many buildings, flipped vehicles and downed trees and power lines.

The University of Arkansas for Medical Sciences hospital, the region’s only major trauma centre, declared a level-1 mass casualty alert after the tornado struck Little Rock, the state’s capital and most populous city, on Friday afternoon.

The twister was spawned by one of the numerous violent thunderstorms raking a vast swathe of the United States’ heartland as part of a much larger expanse of extreme spring weather.

Speaking at a late night news conference, Governor Sarah Huckabee Sanders said the tornado claimed at least two lives in Wynne, Arkansas, about 160km east of Little Rock near the Tennessee border.

Some 30 injured people in Little Rock were transported by fire department and other emergency personnel to area hospitals, Mayor Frank Scott Jr told reporters, adding that “by the grace of God, we have not experienced any fatalities”.

Police said several areas in the western end of the city were hardest hit and the mayor described property damage as “extensive”.

Deaths and injuries

Separately, Baptist Health Medical Center in the adjoining town of North Little Rock reported treating 11 patients from the storm, one of them in critical condition.

Local television station KTHV-TV reported one storm-related death in North Little Rock but that could not be immediately confirmed.

Between five and 10 other patients were treated at the emergency department of the Unity Health hospital in nearby Jacksonville, administrator Kevin Burton said.

Wynne Police Chief Richard Dennis was quoted by television station KAIT8-TV in Jonesboro, Arkansas, as describing the storm’s aftermath in his town as “total destruction”, with dozens of people trapped in debris.

Aerial footage posted by The Weather Channel showed a heavily damaged area of Little Rock spanning several blocks with numerous homes missing roofs and walls, some of them collapsed, and overturned vehicles littering streets.

The turbulent weather came one week after a previous swarm of thunderstorms unleashed a deadly tornado that devastated the Mississippi town of Rolling Fork, destroying many of the community’s 400 homes and killing 26 people.

Video shot on Friday from a window in a Baptist Health facility and verified by Reuters showed a towering, swirling black column of air, moisture and dust moving slowly through the landscape in the near distance.

Governor Sanders said she had mobilised about 100 National Guard troops to assist in the ememrgency response and signed an executive order to immediately authorise $US250,000 ($A373,972) from the state disaster response and recovery fund.

Twisters by the dozen

The twister struck as a blast of extreme spring weather swept much of the United States, menacing the nation’s midsection from Texas to the Great Lakes with thunderstorms and tornados.

The National Weather Service was tracking at least three dozen unconfirmed tornado reports in Arkansas, Tennessee, Illinois and Iowa.

Tens of millions of Americans across the Great Plains, Midwest, South and East were under warnings and advisories for various weather hazards on Friday evening and into the weekend, the NWS said.

Besides Arkansas, southern Missouri, western Kentucky and western Tennessee were deemed at greatest risk of severe thunderstorms capable of producing violent tornados, large hail and damaging winds, the weather service said.

-AAP