"The train was en route from the northeastern city of Mashhad to Tehran. So far 10 passengers have been killed and dozens wounded," the semi-official Fars news agency reported. "The death toll is expected to rise."
A local official said the train carried 340 passengers.
State television said the cause of the crash was under investigation by authorities.
The Students News Agency ISNA put the death toll at two and said four people were in critical condition.
In 2004, a runaway train laden with fuel and fertilizers derailed in northeastern Khorasan province, exploded and burst into flames, killing about 300 people.