Violent storms unleashed tornadoes, high winds and hail in four central US states and killed eight people in Arkansas, including a teenager who died when a tree fell into her bedroom as she slept.

The storms late Friday and early Saturday ripped off roofs and toppled train cars near Kansas City, Missouri; pelted parts of Oklahoma with hail; and knocked over tents at a popular open-air market in east Texas. Severe thunderstorms were moving into Kentucky and could make for a wet Kentucky Derby on Sunday.

Greg Carbin, a meteorologist for the national Storm Prediction Centre in Norman, Oklahoma, said as many as 25 tornadoes may have cut through stretches of Oklahoma, Arkansas, eastern Kansas and western Missouri.

Six of those killed were in two north-central Arkansas counties, Conway and Van Buren, that also had fatalities from a devastating tornado on February 5.

A father and two sons died in Conway County when a possible tornado hit their mobile home. A twister demolished a chicken farm in Center Springs, leaving thousands of dead birds on the ground.

Near the Oklahoma line in a working-class neighbourhood of Siloam Springs, a 15-year-old girl died in the early morning when apparent straight-line winds toppled a tree into her family's mobile home. She and her 10-year-old brother were sleeping in bunk beds; the boy survived with minor injuries.

"She was on the top bunk. He was on bottom. When it fell it just crushed her and pinned her on top of him," with a mattress between them, said Chad Tilghman, who lives across the street and helped pull the boy from the storm debris.

Tornadoes appeared to touch down in at least three east Texas towns, uprooting trees, flipping cars and yanking down power lines.

At least three tornadoes raked central and northern Oklahoma, including one in Osage County near Tulsa that was an estimated 100 metres wide, but no serious injuries were reported there. A home was destroyed and about a dozen others were damaged in north-eastern Oklahoma, and a hotel under construction near Tulsa was destroyed.

The storms moved into Kentucky and Tennessee this evening and other severe weather developed in Illinois, forcing the cancellation of more than 200 flights at Chicago's busy O'Hare International Airport.

A day before the Kentucky Derby, some race fans at Churchill Downs sought shelter when the storms arrived in Louisville. The Weather Service issued a tornado warning for parts of far western Kentucky, and meteorologist John Gordon said two more waves of storms were expected Saturday night and Sunday afternoon.