"After spotting the drone, our air defence system missiles shot it down," Farzad Fereidooni, commander of an anti-aircraft system in Kermanshah province was quoted as saying by IRNA.
Asked if it belonged to the United States, a spokesman for U.S. Central Command said: "The Department of Defense can confirm all of its remotely piloted aircraft are accounted for."
In recent years, Iran has downed U.S. surveillance drones and what it claimed to be an Israeli spy drone.
Fereidooni said Iran had on 12 occasions over the last year issued warnings to unidentified planes that subsequently left Iranian air space.