The US's handover of Camp Cropper to Iraq on Thursday marks a milestone in the country's road to full sovereignty, as well as the end of a troubling chapter in the US's presence in Iraq.

But the attacks were a reminder of the challenges confronting Iraq.

Authorities said a car bomb targeting a police patrol killed a senior officer, two policemen and three civilians in the city of Tikrit. Eleven civilians were wounded.

Earlier, a bomb on a Baghdad minibus left two dead and another five people wounded.