Baghdad ? A suicide bomber armed with an assault rifle opened fire on worshippers during Friday prayers at a mosque in northern Iraq until he ran out of ammunition and then blew himself up, killing 12 people, police and hospital officials said.

The dead included the Sunni cleric who was leading the prayers at the mosque in Tal Afar, but it was unclear if he was the intended victim, said a local police official. Sunni clerics who have been speaking out against al-Qaida in Iraq and sectarian violence have increasingly become targets for attacks.