Iraqi authorities say a bomb has killed four people and wounded nine others at a security checkpoint in eastern Baghdad.

Police and medics say the dead include three Iraqi police commandos and a member of an armed Sunni group that has turned against Al Qaeda in Iraq.

The injured include seven Iraqi security personnel and two bystanders.

The police and medics spoke about the attack Saturday on condition of anonymity because they are not authorized to speak to the media.

On Friday, a car bomb ripped through a crowded commercial district in Dujail, a mainly Shiite town north of Baghdad. Iraqi officials say at least 32 people died.