Al-Qaeda front group the Islamic State of Iraq and the Levant has claimed a wave of attacks that killed 91 people and injured hundreds during the Eid al-Fitr holiday on Saturday.
"The Islamic State mobilised... in Baghdad and the southern states and others to convey a quick message of deterrence on the third day of Eid al-Fitr" in response to security forces' operations, a statement posted on forums late on Sunday said.
Iraqis have angrily blamed the authorities for failing to prevent a series of deadly bombings and other attacks on Saturday, which came as the country marked the end of the Muslim holy month of Ramadan, its deadliest in years.
The attacks came just weeks after assaults on prisons near Baghdad, also claimed by the al-Qaeda front group, freed hundreds of prisoners including leading fighters, prompting warnings of a surge in violence.
Nine people were killed in fresh violence around the country on Sunday.
Gunmen opened fire at a checkpoint manned by Sunni armed group, killing two and wounding two in the town of Buhriz, about 60km northeast of Baghdad, police said.
Further north, gunmen attacked a busy park in the town of Balad, killing two and wounding three, police said.
Three anti-terrorism squad officers were killed and nine wounded by a roadside bomb in the town of Mahaweel, according to police sources.
The United States condemned Saturday's string of car bombings that targeted markets, cafes and parks crowded with people celebrating Eid al-Fitr holidays.
The State Department said Saturday's attacks bore the hallmarks of al-Qaeda's Iraqi (AQI) branch.
It reiterated that it was offering a $10 million reward for information leading to the killing or capture of Abu Bakr al-Baghdadi, the AQI leader.
Last month al-Qaeda claimed responsibility for simultaneous raids on two Iraqi prisons and said more than 500 inmates had escaped in the brazen operation.