(Reuters) - A mile-wide tornado has touched down west of Oklahoma City where it has done damage and it is headed toward Oklahoma City, Oklahoma television station KFOR reported.

The tornado overturned vehicles and did damage along Interstate 40, the station reported. The National Weather Service has declared a tornado emergency, which is more severe than a warning, for the area.

(Reporting by Alex Dobuzinskis; Editing by Cynthia Johnston)