Officials fear all on board an Iranian commercial aeroplane that crashed in a foggy, mountainous region of southern Iran have died.

The plane, which was carrying 65 people, was only brought back into service months ago after being grounded for seven years.

The crash of the Aseman Airlines ATR-72 marks yet another fatal aviation disaster for Iran, which for years was barred from buying airplane parts for needed maintenance due to Western sanctions over its contested nuclear programme.

Its nuclear accord with world powers allows it to get those parts and the country has made deals worth tens of billions of dollars for new aircraft. However, US President Donald Trump’s refusal to re-certify the deal has injected uncertainty into those sales while Iranians still fly in ageing aircraft.

The ATR-72, a twin-engine turboprop used for short-distance regional flying, went down near its destination of the southern Iranian city of Yasuj, some 485 miles south of the Iranian capital, Tehran, where it took off.

It is not clear what caused the crash, although weather was severe in the area. Dense fog, high winds and heavy snow in the Zagros Mountains made it impossible for rescue crews in helicopters to reach the site on Sunday, state television reported.

Aseman Airlines spokesman Mohammad Taghi Tabatabai told state TV that all on board Flight No. EP3704 were killed. Those on board included 59 passengers and six crew members, the state-run IRNA news agency reported on Sunday night, lowering the death toll to 65 from an initially reported 66.

“After searching the area, we learned that unfortunately … our dear passengers had lost their lives,” Mr Tabatabai said.

Both Supreme Leader Ayatollah Ali Khamenei and President Hassan Rouhani offered their condolences.

Mr Tabatabai said the plane crashed into Mount Dena, which is about 4,400 meters (14,435 feet) tall. The plane’s last signal, at 0555 GMT, showed it at 16,975 feet and descending, according to airplane-tracking website FlightRadar24. The pilot was in contact with the tower 14 miles from the airport, state TV said.

One previous passenger on the route posted a video on Sunday showing that the flight typically comes in just over the mountain peaks. Aeronautical charts for the airport warn pilots to keep an altitude of 15,000 feet in the area. The airport itself is at nearly 6,000 feet.

The Iranian Red Crescent said it has deployed to the area. Locals described hearing the crash, although no one had found the crash site yet, according to state TV.

Aseman Airlines, owned by Iran’s civil service pension foundation, is a semi-private air carrier headquartered in Tehran that specialises in flights to remote airfields across the country. It also flies internationally.

Aseman Airlines is Iran’s third-largest airline by fleet size, behind state carrier Iran Air and Mahan Air. However, it is banned from flying in the European Union over safety concerns.

The carrier has a fleet of 29 aircraft, including six ATR aircraft, according to FlightRadar24. The ATR-72 that crashed on Sunday, with the tail number EP-ATS, had been built in 1993, Aseman Airlines CEO Ali Abedzadeh told state TV.

On Instagram, Aseman Airlines highlighted the doomed aircraft in October, saying it had been “grounded” for seven years but would be “repaired and will be operational after checking and testing”. It was not clear what led to the grounding, though Iran only recently regained access to the airplane parts market after the nuclear deal.

European airplane manufacturer ATR, a Toulouse, France-based partnership of Airbus and Italy’s Leonardo SpA, said it had no immediate information about the crash.

AP