Ten people were killed on Wednesday when a rescue helicopter ferrying wounded people from a vehicle accident to hospital hit power lines and crashed to the ground in northeastern Iran, media reported.
Those who died included four members of the helicopter crew, five people who had been wounded in the minibus crash and a doctor from the emergency services.
"Eight people were killed on the spot and two people wounded in the crash died later in hospital," local emergency medical services official Reza Vafaeenejad told the ISNA news agency.
The report quoted an emergency services official in Mashhad as saying the rescue chopper was taking people wounded in a vehicle accident to hospital in the city when it hit high voltage power lines in thick fog.
The "helicopter belonged to the air force and was on lease to the emergency services," the official said.
Iran is subject to harsh sanctions from Western countries over its disputed nuclear programme, with spare parts for its military aircraft fleet as well as for civilian planes affected.