Sky News
The accident happened when the train, en route from Iran's northeastern city of Mashhad to Tehran, hit a maintenance train on the line near the town of Varamin, reports say.
According to the Iranian Labor News Agency (ILNA), three people have been killed in the accident.
The incident comes just a day after a passenger plane skidded off a runway in northeast Iran, killing at least 17 people.
Footage from Iranian TV showed the plane sitting at an angle, its tail awkwardly on the ground and the mangled front end pointing upward.
The Russian-made Ilyushin-62 Aria Airlines plane was carrying 153 passengers and flew from the capital Tehran to the northeastern city of Mashhad.
And on July 15, an Iranian passenger plane crashed shortly after take off, killing all 168 people on board.
Meanwhile, turmoil continues to hit Tehran following disputed presidential elections in the country last month.
Iranian police and pro-government militia attacked and scattered hundreds of protesters who had gathered in Iran's capital in response to global demonstrations of solidarity that have been taking place, witnesses said.
Demonstrators in Vanak and Mirdamad districts chanted "death to the dictator" and "we want our vote back" before reportedly being attacked and beaten by police.
