An Iranian passenger plane with 66 people on board has crashed in central Iran during a flight from Tehran to the city of Yasuj, according to Iranian news media reports.

A spokesperson for Iran Aseman Airlines told state TV that Sunday's air crash killed all 66 people on board.

The plane went down in a mountainous area near the town of Semirom, the news agency ISNA quoted Mojtaba Khaledi, emergency services spokesperson, as saying.

The Iranian Red Crescent said it had deployed to the area, which was quite foggy at the time of the crash.

State-run PressTV said the Iran Aseman Airlines flight was carrying 60 passengers and six crew members.

Aseman Airlines is a semi-private air carrier headquartered in Tehran that specialises in flights to remote airfields across the country and also flies internationally.

The ATR-72, a twin-engine turboprop, is used for short-distance regional flying. Authorities said they would be investigating the crash.

Under decades of international sanctions, Iran's commercial passenger aircraft fleet has aged, with air accidents occurring regularly in recent years.

Following the 2015 nuclear deal with world powers, Iran signed deals with both Airbus and Boeing to buy scores of passenger planes.

Speaking to Al Jazeera from London, David Learmount, aviation safety specialist and former pilot, said: "Weather in the mountains where the plane crashed was pretty bad.

"It looks as if, when the aircraft was carrying out its initial descent towards its destination, it was in the wrong position and it hit mountains.

"Basically, it's a failure of navigation. An airplane hitting mountains in clouds is like a ship hitting rocks."

According to Learmount, the jet that crashed was "a very well-tested airplane [model]", but the carrier was not unfamiliar with accidents in Iran's difficult terrain.

"The Iran Aseman Airlines flies through lot of difficult terrain of the country. It is more exposed to risk just by the virtue of the country that Iran is."

PHOTO CAPTION

Map of Iran locating city of Yasuj

Al-Jazeera