The report said a twister that touched down late in the afternoon in Ottawa County, Oklahoma, killed six people and heavily damaged many buildings.
In nearby Picher, Oklahoma, several people remained unaccounted for, according to the network.
An unspecified number of residents were injured when a tornado touched down between the towns of Seneca and Neosho near the Missouri-Kansas border, CNN reported.
Ten people were killed in the community of Racine in Newton County, Missouri, the network said, citing local emergency officials.
Another person perished when thunderstorms knocked a tree onto a mobile home east of Carthage, Missouri, according to the report, and one more weather-related death was reported in Purdy, Missouri.
Authorities fear there may be additional casualties in Missouri, CNN noted.