A string of bomb attacks and shootings in Baghdad and north of the capital has killed at least 91 people, say security and medical officials.
Many of those killed were security forces - who appear to have been a prime target, correspondents say.
One of the worst-hit places was Taji, a Sunni neighbourhood some 20km (12 miles) north of Baghdad, where at least 24 people were killed.
At least 172 people were wounded on one of the bloodiest days of the year.
Some 13 Iraqi towns and cities were hit in the spate of apparently co-ordinated attacks.
Deadly bombings hit Shia districts in Baghdad. In the deadliest attack, a car bombing at a government building in Sadr city killed at least 12.
At least seven car bombs hit the northern oil city of Kirkuk.
Dhuluiya, Saadiya, Khan Beni-Saad, Tuz Khurmatu and Dibis were also said to have suffered attacks.
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What is the guilt of these poor people?”
In pictures: Deadly attacks across Iraq
The attacks come days after a man purporting to be Abu Bakr al-Baghdadi, the leader of al-Qaeda in Iraq, declared a new offensive to retake areas it retreated from before US soldiers left the country last December.
"The majority of Sunnis in Iraq support al-Qaeda and are waiting for its return," the man said, according to Associated Press, in an audio message posted on militant websites.
BBC News - Iraq: Wave of attacks in Baghdad and north 'kills 91'