It is understood the smash happened in subzero temperatures when a moving train hit a stationary one at Haft-Khan station in the city of Shahroud in Semnan province on Friday.
Footage showed some of the carriages on fire as rescue teams attempted to put out the blaze and search for survivors.
The collision reportedly caused four carriages to come off the tracks.
The injured were taken to nearby hospitals amid fears the number of fatalities and casualties could rise.
The province’s Red Crescent director, Hassan Shokrollahi, said: “We do not have the exact number of those killed as the train is on fire.”
He said the remote location of the station was also complicating rescue efforts.
“Due to the difficulty of access, only our helicopter has managed to reach the scene,” he said.
The cause of the collision is being investigated.