At least 36 people were killed in a train crash in the northern Iran province of Semnan on Friday.

More than 70 people were hospitalized after a passenger train rammed into the back of a broken-down intercity express near the city of Shahroud, provincial governor Mohammad Reza Khabbaz said.

A mechanical failure, possibly caused by cold weather, forced the Tabriz-Mashad express train to stop between stations on the main line between Tehran and Mashhad, Khabbaz said.

Two of the express train carriages burst into flames after the 7:50am crash (04:20 UTC).

The front four carriages of the second train - running from Semnan to Mashhad - derailed and overturned.

"One minute I was sleeping and the next I was being carried out of a coach on fire," one hospitalized passenger told state television.

Firefighters were working to control the blaze, a spokesman for Iran's Red Crescent, Mostafa Mortazavi told the semi-official Fars news agency.

Authorities said cold weather could have caused the mechanical failure that stalled the intercity express train

The Red Crescent provincial chief told state TV the remote location of the crash had slowed rescue efforts. "So far only one helicopter has reached the scene because of access difficulties," said Hasan Shokrollahi. Injured passengers were taken to hospitals in Semnan and Damghan. The death toll is expected to rise.

Years of punitive sanctions imposed over Iran's nuclear program means its railway network has deteriorated. Sanctions were lifted in January under a deal that curbed its nuclear activity.

About 17,000 people die in traffic accidents every year in Iran.

aw/kl (Reuters, AFP, AP, dpa)