Reports said the blast, near the Imam al-Abbas Mausoleum, appeared to be Sunni retaliation in the latest in a series of tit-for-tat sectarian attacks.
A man identified as Kefah described the scene following the explosion. "They shouted at the driver of the pickup truck and told him to move the car, but he did not move. The car has a government number plate. Seconds later the car went off," Kefah said.
Meanwhile, three people were killed and three wounded in a car bomb blast in the northern city of Mosul. There were no further details.