A truck bomb ripped through a petrol station where buses packed with Shiite pilgrims returning from the Arbaeen commemoration in the Iraqi city of Karbala were parked Thursday, police officials said.

"At least seven buses with pilgrims were inside the petrol station at the time," a police lieutenant colonel told AFP.

The blast struck in the village of Shomali, 120 kilometres (75 miles) southeast of the capital Baghdad.