Iraqi police said at least four people were killed when a bomb attached to a vehicle exploded in restive Diyala province.
Friday's attack took place in the town of Khalis, north of Baghdad.
Elsewhere in Diyala, police said a bomb planted on a motorcycle in the town of Baqouba killed the leader of a government-backed Sunni militia. At least three other people were wounded in that blast.
The militias fight al-Qaida and other groups and have been credited with helping reduce violence in Iraq.
In other news, the U.S. military said a coalition soldier was killed when a grenade exploded near a military patrol in Nineveh province in northern Iraq.
Some information for this report was provided by AFP, AP and Reuters.