A train collision in northern Iran killed at least 43 people and injured 100 on Friday, Iran's state media reported.

The official IRNA news agency quoted Mostafa Mortazavi, a spokesman for the country's Red Crescent, as saying the latest casualty figures had risen to 43 killed in the accident that occurred in sub-zero temperatures when a moving passenger train struck another parked at Haftkhan station about 250 kilometres east of the capital Tehran.

The report said four of the fatalities were railway employees who were on the two trains when the accident happened near the city of Semnan.

The TV said that in the collision, four carriages derailed and two caught fire. It showed footage of rescue teams working near train carriages on fire. The casualties from the crash were taken to nearby hospitals.

Initial reports had put the death toll at eight but the provincial governor, Mohammad Reza Khabbaz, later told state TV that more bodies were recovered at the scene of the crash.

This picture released by Iranian Fars News Agency shows the scene of two trains collision about 250 kilometres east of the capital Tehran, Iran, on Friday. (Saeed Esmaeilpour/Fars News Agency/Associated Press)

Not inside station

Khabbaz said the cause of the accident was under investigation and that the parked train was apparently not inside the station but on a main rail line at the time of the collision.

The TV report said that 95 people who were injured in the collision were all in hospital. It said many of them only suffered minor injuries.

Earlier, Ali Asghar Ahmadi, head of Iran's Red Crescent, told state TV that the death toll may raise further, based on unconfirmed reports from the site.

Helicopters and ambulances were sent to join the rescue operation, Ahmadi added.

Iran reports about 17,000 deaths on average in traffic accidents every year. The high accident rate is mostly blamed on drivers disregarding traffic laws, old vehicles and inadequate emergency services.

Years of punitive international sanctions against Iran over its controversial nuclear program have also badly affected Iran's infrastructures, including road and the railway network.