Insurgents attacked a Shiite mosque and a police station in separate incidents in Baghdad on Friday.
Thirty people died in the attacks, including at least 16 Iraqi security personnel.
Jordan-born militant Abu Musab Al Zarqawi's Sunni rebel group, Al Qaida in Iraq, claimed responsibility for the attacks.
The militant organisation's claim appeared on an Islamic website. "The destructive effect of such operations on the morale of the enemy is clear," the message said.
The attacks occurred in the Sunni Muslim stronghold of Azamiyah, where a car bomb exploded during a clash between Iraqi security forces and rebels near a Shiite mosque.
Azamiyah was a major centre of support for Saddam Hussein. Initial reports had suggested that the bomb targeted a police station.