Two passenger trains collided in Iran's north-central province of Semnan on early Friday, killing at least five people and injuring over 20 others, Iran's state television reported.

"So far the death toll has reached to five. Some 20 passengers have been injured and transferred to nearby hospitals," the television reported, without giving details on the number of passengers in the trains.

The report showed footage of four derailed carriages, with two of them on fire.

"The accident happened when a passenger train in motion crashed to another one that had stopped at the station," it said.

The cause of the collision was under investigation, it said, adding that rescue teams have been dispatched to the site of accident.

The crash occurred at the Haft-Khan station in the city of Shahroud, about 400 kilometers (250 miles) east of Tehran.