A plane crash in southern Iran has killed all 66 people on board, according to a spokesman for Aseman Airlines.
According to media reports the plane has been identified as an ATR-72, which crashed near the remote mountain town of Semirom, some 620km south of Tehran.
Rescue helicopters were unable to reach the site in the Zagros Mountains because of fog, state TV reported.
The Russian Embassy in Tehran is verifying whether Russian nationals were on board of a plane that crashed in Iran, the Russian Foreign Ministry said Sunday.
After the 2015 nuclear deal, the country signed deals to buy new passenger planes, including a $536m (£382m) deal with ATR last April for at least 20 aircraft.
"All emergency forces are on alert", an emergency services spokesman said.
Authorities said the plane was flown by Aseman Airlines, a semi-private air carrier headquartered in Tehran that specializes in flights to remote airfields across the country.
Mehrabad is located in western Tehran and mainly functions as a domestic airport, although it also serves some global routes.
The Iranian Red Crescent said it has deployed to the area, which was quite foggy at the time of the crash.