The blast went off Saturday, as pilgrims were returning from a religious ceremony.

Police and hospital officials said on Sunday that 64 people were wounded in the attack in Samarra, 60 miles (95 kilometers) north of Baghdad

The officials did not want to be identified because they were not authorized to speak to the media.

The bomber blew himself up on a bus carrying pilgrims back from the al-Askari mosque which has been a flashpoint for bloodshed in the past. A 2006 bombing by Sunni insurgents destroyed its golden dome and sparked retaliatory bloodshed between Sunnis and Shiites.