A trailer-truck smashed one of the gates at an important place of worship in Iran's Shiite holy city of Qom on Sunday and its driver was arrested, Fars news agency said.

It was not immediately clear whether the incident was accidental or deliberate.

"A truck destroyed gate number six of the holy mosque of Jamkaran and entered the precincts of the sacred place," Fars said, without specifying whether there had been any casualties.

It added that the truck was carrying extra gasoline, but did not specify what led to the incident.

The Jamkaran mosque, which welcomes thousands of pilgrims every week, was built on the spot where most Shiites believe the Mahdi, the twelfth imam of Shiite Islam, will return. They believe he disappeared more than a thousand years ago and will return one day to usher in a new era of peace and harmony.

After the incident, pilgrims were evacuated and law enforcement personnel established a security cordon, Fars added.