The collision in Semnan province on the main line between second city Mashhad and the capital Tehran also injured 11 people, the television said.

The province's Red Crescent director, Hassan Shokrollahi, said the death toll could rise.

"We do not have the exact number of those killed as the train is on fire," he said.

"Due to the difficulty of access, only our helicopter has managed to reach the scene," he said.