An Iranian jetliner skidded off the runway and burst into flames in the northeastern city of Mashhad on Friday, killing at least 29 of the 148 people on board, Iran's aviation chief said.

The plane slid off the runway, "then its left wing hit the ground and caught fire," Nourollah Rezai Niaraki, chairman of Iran's Civil Aviation Organization, said in a TV interview.

Iran's state television had earlier reported that 80 people had died in the accident involving the Russian-made Tupelov 154.

Dozens were rescued from the flight -- operated by Iran Airtour -- which landed in the northeastern Iranian city of Mashhad from Bandar Abbas.

The flight crew and pilot were not killed in the accident, Roads and Transport Minister Mohammad Rahmati told Iran's students news agency ISNA.

"This will be a great help to find out the cause of the accident as soon as possible," Rahmati said.

The condition of the evacuated passengers is unclear.

"Because some of the injured have been transferred to hospitals, we have no exact figures about the death toll," the managing director of Iran Airtour, Mehdi Sadeqi, told state television.

Images from the crash site showed rescue workers carrying bodies on stretchers from the wreckage of the plane. The cockpit appeared to be largely unaffected.

Iran has a poor aviation safety record, air safety experts say, and has suffered a string of crashes in recent decades.

In one of the deadliest aviation accidents in Iran's history, an Iranian Illyushin-76 troop carrier crashed in southeastern Iran in February 2003, killing all 276 Revolutionary Guard soldiers and crew aboard.

In December 2005, an Iranian Air Force C-130 aircraft crashed into a 10-storey apartment block in Tehran, killing all 94 people on board and at least 22 people on the ground.

Due to U.S. sanctions, Iran has been forced to rely on aircraft from the former Soviet Union to bolster its aging fleet of Boeing and Airbus planes.

With files from The Associated Press