The semi-official Fars said the plane was a US Falcon, while state TV said it belonged to a European aid agency.

Both reports said those on board were released a day later, without saying when the event happened.

The Pentagon denied any of its aircraft had been involved in such an incident, saying all were accounted for and that none had landed in Iran.

The Fars report said the aircraft entered Iranian airspace from Turkey, flying at low altitude to avoid radar.

It said the plane was intercepted by Iranian fighter jets and forced to land at an undisclosed airport.

It said its occupants were released a day later after it became clear they had entered the country unintentionally.

BBC