Updated

An Iranian news agency says a helicopter belonging to the country's air force has crashed north of Tehran, killing all three crew members on board.

Thursday's report by the semi-official Fars news agency quotes a district governor, Ezzatollah Khammohammadi, as saying that rescue teams have rushed to the crash site in the mountains north of the Iranian capital.

He says the cause of the crash is not immediately known and that an investigation is underway.

The report did not identify the victims or give the type of helicopter involved. Iran's military has both American and Russian-made helicopters in service.

Iran has a history of frequent air accidents blamed on its aging aircraft and poor maintenance. The area north of Tehran experienced snowfall and low visibility on Thursday.