Here are details of some of the major attacks in Iraq in the past year:
March 29, 2011 - At least 53 people are killed and 98 wounded when gunmen take hostages at a provincial council headquarters in Saddam Hussein's hometown of Tikrit, precipitating a battle with security forces who sweep in to end the siege.
August 15 - A wave of attacks strike cities across Iraq, killing around 70 people and wounding more than 200 in the bloodiest day yet in 2011.
- In the worst attack, a roadside bomb followed by a car bomb targeting police kills at least 37 people in Kut, 150 km (95 miles) southeast of Baghdad. Other deadly attacks take place in Tikrit, Najaf, Diyala and Kerbala.
August 28 - A bomber wearing a cast on his arm blows himself up in the main hall of the Umm al-Qura mosque, an important Sunni religious site in Baghdad. At least 32 people are killed and 39 wounded.
December 22 - More than 10 coordinated bombings strike Baghdad, killing at least 72 people, with around 200 wounded.
- In one of the attacks, at least 18 people are killed when a suicide bomber detonates an ambulance he was driving near a government office in the Karrada district. More bombs explode in the central Alawi area, Shaab and Shula in the north, all mainly Shi'ite areas.
- The Islamic State of Iraq, an umbrella group for al Qaeda-linked insurgents, claims responsibility.
January 5, 2012 - Four bombs in mainly Shi'ite Muslim areas of Iraq kill at least 73 people with around 150 people wounded.
- The biggest attack takes place beside a police checkpoint west of Nassiriya in the south, where a suicide bomber targeting Shi'ite pilgrims kills 44 people.
January 14 - A suicide bomber disguised as a policeman kills at least 53 people and wounds 130 more in an attack on Shi'ite pilgrims at a police checkpoint in Basra, southern Iraq.
January 27 - A suicide bomber explodes his vehicle near a passing Shi'ite funeral procession in the Zaafaraniya neighborhood of Baghdad, killing at least 31 and wounding more than 60 others, police say.
February 23 - At least 65 people have been killed in bomb blasts across Iraq. Thirty-two people are killed in Baghdad where 10 explosions tear through mainly Shi'ite neighborhoods. The remaining casualties are killed in blasts across the country.
(Reporting by David Cutler, London Editorial Reference Unit)