Iran's Fars news agency said Iranian fighter jets had forced a U.S. military aircraft to land in Iran after it had entered its air space without permission.
It said there were five military officers and three civilians on board the aircraft and that they were held for questioning and allowed to leave a day later.
The Pentagon said it was not aware of any missing military aircraft or personnel.
"All aircraft in the region are accounted for and we have no reports of any aircraft landing in Iran," Lt. Col. Patrick Ryder told reporters, according to Reuters.
In a conflicting account, Iran's Al-Alam television said the aircraft was not military and belonged to Hungary.
The White House also cast doubt on the Iranian reports, saying it had no reason to believe they were correct.
"We're looking into the various and conflicting reports coming from the Iranian 'news' agencies, but do not have any information at this time that would lead us to believe they are correct," spokesman Gordon Johndroe said.
Al-Alam said the plane, en route from Turkey to Afghanistan, strayed off course, was forced to land Sunday and allowed to fly to Afghanistan on Monday.
