Most of the Oklahoma fatalities occurred in the Oklahoma City metropolitan area. Cherokee Ballard, a spokeswoman for the Oklahoma Medical Examiner's office, said early Wednesday that the storms killed five people in Canadian County, two in Logan County and one in Grady County.
Ballard said a child was among those killed, but she had no other details.
At least three people died as the storms bombarded Arkansas' Franklin and Johnson counties.
Department of Emergency Management spokesman Tommy Jackson said one person died after a tornado raked across the tiny western Arkansas community of Denning early Wednesday, and another died in an area called Bethlehem, in Johnson County.
Franklin County's chief deputy sheriff, Deputy Devin Bramlett, said early Wednesday that one person also died in the community of Etna.
Several people were also injured in Franklin and Johnson counties. A rural fire station in Franklin County was left without a roof as emergency workers rushed to the wounded. Downed trees and power lines tossed across roadways also slowed search-and-rescue crews' efforts.
In Kansas, police said two people died when high winds threw a tree into their van around 6 p.m. near the small town of St. John, about 100 miles west of Wichita. The highway was shut down because of storm damage.