The Arkansas Department of Emergency Management said there were eight storm-related fatalities, while an official with the Oklahoma Emergency Management Agency said there were at least two tornado victims in the state.
Local emergency crews were combing through the debris in some of the hardest-hit towns as forecasters warned that more twisters were on their way.
"It's chaos right now," the mayor of the Arkansas town of Velonia, James Firestone, told CNN.
The downtown area "seems like it's completely levelled. There's a few buildings partially standing, gas lines spewing. Fire lines down. We've had some casualties."
Firestone said that police and firefighters from nearby cities as well as National Guard troops were heading to his town to help.
Pictures of tornado damage posted by Arkansas TV station THV 11 showed overturned cars, homes ripped in half, and houses reduced to piles of debris.
AFP