Officials say a wave of shooting and bombing attacks in Baghdad and north of the Iraqi capital have killed more than 100 people and injured scores of others.
The attacks included strikes at a military base near the town of Dhuluiyah and in the city of Taji, where some 40 people were reported to have died.
Bombings and shooting attacks also occurred in Saadiyah, Khan Beni Saad, Kirkuk, Tuz Khurmatu, and Dibis, all north of the capital.
Police checkpoints were hit by car bombs, army bases were struck by mortar fire, and one police officer was attacked in his home.
Officials said that in addition to those killed, at least 200 people were wounded as a result of the 21 different attacks mounted in 13 cities.
Reports say the carnage marks the deadliest single day of violence in Iraq this year.
Though there was no immediate claim of responsibility, Al-Qaeda has previously claimed similar waves of attacks. The Sunni militant group has recently warned it was poised to carry out a new offensive.
The July 23 attacks struck mostly at security forces and government officials -- two of Al-Qaeda's frequent targets in Iraq.
The violence has shattered a relative calm that had prevailed in the run-up to the July 21 start in Iraq of the holy Muslim fasting month of Ramadan.
Iraq has in recent months seen several waves of attacks that have killed and wounded scores.
At least 39 people were killed on July 3, many in a truck bombing at a market in central Iraq,
And a wave of apparently coordinated bombings and shootings rocked Iraq on June 13 during a major Shi'ite religious commemoration, killing at least 72 people and wounding more than 250, many of them pilgrims.
On July 22, Al-Qaeda's front group in Iraq said it would begin targeting judges and prosecutors and would try to help its members break out of Iraqi jails.
A message posted on jihadist forums said the Islamic State of Iraq (ISI) would seek to retake territory it ceded before the withdrawal of U.S. combat troops from the country last year and appealed for Sunni tribes to provide support and send fighters.
The voice on the audio message -- purportedly that of leader Abu Bakr al-Baghdadi -- declared that the the group is "starting a new stage."
Al-Qaeda in Iraq is regarded by Iraqi officials and terrorism experts to be significantly weaker than at the peak of its strength in 2006 and 2007.
With reporting by AP, AFP, and BBC