A foreign aircraft has been forced to land in Iran after violating Iranian airspace, Iranian media say.
State Al-Alam TV said the aircraft was Hungarian and not American, discounting earlier reports by Iran's semi-official Fars news agency.
The aircraft and those on board were allowed to continue their journey after being questioned, the reports said.
The Pentagon denied any of its planes had been involved in such an incident and said none had landed in Iran.
"All our aircraft are accounted for and we have no reports of any aircraft landing in Iran," Lt Col Patrick Ryder told reporters.
White House spokesman Gordon Johndroe said officials were checking the "various and conflicting" Iranian reports.
It comes at a time of heightened tension between the United States and Iran over Tehran's nuclear programme.
The US severed diplomatic ties with Iran in 1980 after US nationals were taken hostage by Iranian radicals in Tehran.
The Arabic-language Al-Alam TV quoted an unnamed senior military official as saying the plane landed at Mehrabad airport on 30 September.
The official said the aircraft was a Hungarian aid plane which strayed into Iranian airspace.
Initial reports from Fars said it was an American plane and was carrying eight people, including five senior US generals.
It said the plane was intercepted by Iranian fighter jets and forced to land at an unspecified airport.
Iranian media said those on board were freed the following day and the plane was allowed to complete its journey to Afghanistan.