People stand in front of a destroyed business in Wynne, Ark., on Saturday. AP

The death toll from a major storm system that has lashed the south-central and eastern US with devastating winds and powerful tornadoes has risen to 26, officials said on Saturday.

Storms that dropped possibly dozens of tornadoes killed at least 26 people in small towns and big cities across the South and Midwest, tearing a path through the Arkansas capital, collapsing the roof of a packed concert venue in Illinois and stunning people throughout the region Saturday with the damage's scope.

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A spokesperson for the emergency management agency in Tennessee, one of the states hardest hit by storms that have struck since Friday, confirmed seven weather-related fatalities to the media.

That came on top of 14 deaths reported in Arkansas, Mississippi and Alabama in the south, and Indiana and Illinois in the Midwest. The storm system on Saturday was bearing down on the US east coast, with thunderstorms, hail and powerful winds predicted through late Sunday.

Businesses and vehicles are damaged from a storm in Little Rock, Ark., on Saturday. AP

Residents of Wynne, a community of about 8,000 people 50 miles (80 kilometres) west of Memphis, Tennessee, woke Saturday to find the high school's roof shredded and its windows blown out. Huge trees lay on the ground, their stumps reduced to nubs. Broken walls, windows and roofs pocked homes and businesses.

Debris lay scattered inside the shells of homes and on lawns: clothing, insulation, toys, splintered furniture, a pickup truck with its windows shattered.

On Friday, the storm had sent multiple tornadoes — some of exceptional size and power -- sweeping through Arkansas, including in the capital Little Rock, where they killed at least five people, the state's governor said.

Daylight revealed extensive damage, with several homes torn apart, cars overturned, power lines toppled and trees ripped out of the ground.

Family and neighbours look through debris on Ed Whestine's farm southwest of Wellman, Iowa on Saturday. AP

Governor Sarah Huckabee Sanders has declared a state of emergency and activated the national guard to help with recovery efforts.

She said she had spoken to President Joe Biden, who had promised to expedite federal aid.

The city of Wynne, in northeastern Arkansas, was "cut in half by damage from east to west," Mayor Jennifer Hobbs told CNN.

The National Weather Service had also issued tornado warnings for several other states, from as far north as Iowa to the southern state of Mississippi, where a twister last week killed 25 people and caused extensive property damage.