Here is a look at the deadliest attacks in Iraq since the withdrawal of U.S. troops on Dec. 18, 2011:

— Dec. 22, 2011: Attackers hit markets, cafes and government buildings in mostly Shiite neighborhoods of Baghdad, killing 69 people.

— Jan. 5, 2012: Coordinated bombings target Shiite Muslims, killing 78 people in Baghdad and near the southern city of Nasiriyah, just days before a Shiite holy day.

— Jan. 14, 2012: A bomb tears through a procession of Shiite pilgrims in southern Iraq, killing at least 53 people.

— Feb. 23, 2012: Attackers kill at least 55 people as car bombs go off near an elementary school in the town of Musayyib, a restaurant in a Shiite neighborhood in Baghdad and various checkpoints and secure areas.

— March 20, 2012: Insurgents bent on derailing an Arab League meeting in Baghdad kill 46 people in attacks on Shiite pilgrims in the holy city of Karbala, bombings in Kirkuk and strikes on security and government officials around the country.

— June 13, 2012: Car bombs target an annual Shiite pilgrimage, killing 72 people in 16 separate explosions.

— July 3, 2012: Bombs pound six cities and towns, killing some 40 people and raising suspicion that security forces may be assisting attacks on Shiites.

— July 23, 2012: Attacks aimed largely at security forces kill 115 people in the country's deadliest single day in two years.

— Aug. 16, 2012: A blistering string of bombings and shootings across the country kills at least 93 people.

— Sept. 9, 2012: Insurgents gun down soldiers at an army post, bomb police recruits waiting in line to apply for jobs and stage other attacks in violence that kills 92 people.

— Nov. 6, 2012: A suicide bomber detonates his explosives-laden car near a military base north of Baghdad, killing at least 33 people.

— Nov. 27, 2012: Insurgents launch attacks against Shiite mosques, security forces, and other targets in central and northern Iraq, killing at least 30 people.

— Jan. 16, 2013: A wave of bombings against the offices of a major Kurdish party and Kurdish security forces headquarters in Kirkuk province kills at least 33 people.

— Feb. 17, 2013: Car bombs tear through shopping areas in Shiite neighborhoods in Baghdad, killing at least 37 people.

— March 4, 2013: Gunmen attack a convoy of Syrian soldiers who had crossed into Iraq for refuge, killing 48 people.

— March 14, 2013: Militants unleash a carefully planned assault on the Justice Ministry, killing 30 people.

— March 19, 2013: Insurgents carry out a wave of bombings that kills at least 65 people on the eve of the 10th anniversary of the U.S.-led invasion. An al-Qaida in Iraq front group claims responsibility.

— April 15, 2013: A string of attacks kills at least 36 people across the country ahead of provincial elections.

— April 18, 2013: A suicide bomber detonates explosives at a Baghdad cafe crowded with young people, killing 32 people.

— April 23, 2013: Security forces storm a Sunni protest camp in the north, sparking deadly clashes in several towns, which combined with other attacks kill 56 people.

— April 25, 2013: More than 40 people are reported killed in fighting in the key northern city of Mosul.

— April 29, 2013: A wave of car bomb blasts tears through Shiite areas south of Baghdad, killing at least 36.

— May 15, 2013: A car bomb goes off near a bus station in Baghdad's main Shiite district, the deadliest of explosions that killed at least 33 people nationwide.

— May 17, 2013: Bombs strike Sunni areas in Baghdad and surrounding areas, killing at least 76 people.

— May 20, 2013: A wave of attacks, some at markets and in rush hour crowds, kills 113 people in Shiite and Sunni areas.

— May 21, 2013: Car bombing at a Sunni mosque kills at least 20 people.

— Aug. 10, 2013: A wave of car bombs in mainly Shiite areas of Baghdad kills at least 60 people as Muslims observe the end of Ramadan.

— Aug. 25, 2013: Insurgents kill at least 46 people in numerous attacks scattered around the country.

— Sept. 15, 2013: A wave of car bombings and other attacks in Iraq kill at least 53 people.

— Sept. 21, 2013: A suicide bomber detonates his explosives-laden car near a funeral tent packed with mourners and another bomber on foot blows himself up nearby in a Shiite part of Baghdad, killing at least 72 people.

— Nov. 7, 2013: A series of attacks in Iraq, including a double suicide car bombing targeting a military base, kills 30 people.

— Jan. 18, 2014: Violence across Iraq, including a series of car bombings and fighting between militants and government troops over control of Anbar province, kills at least 30 people.

— Feb. 18, 2014: A wave of car bombs kills at least 49 people in the Iraqi cities of Baghdad and Hilla.

— April 21, 2014: Suicide bombings and other attacks across Iraq kill at least 33 people.

— May 13, 2014: Militants unleash a wave of car bombings in Iraq, killing at least 34 people in a show of force meant to intimidate the majority Shiites as they celebrated the birthday of Imam Ali.

— Aug. 22, 2014: At least 64 people are killed, including four Shiite militiamen, after gunmen storm a mosque in Diyala province and open fire on worshippers.

— Aug. 23, 2014: Bombings in Baghdad and the northern city of Kirkuk kill at least 42 people.

— Sept. 3, 2014: Human Rights Watch says that militants from the Islamic State group carry out a mass killing of between 550 to 770 Iraqi soldiers captured when the extremists overran the Camp Speicher military base in June. The militant group claims it kills 1,700 in that attack.

— Oct. 11, 2014: A series of car bomb attacks in Shiite areas of Baghdad kills 38 people.

— Oct. 16, 2014: Militants unleash a wave of attacks in Iraq, mainly targeting Shiite areas in and around Baghdad, killing at least 50 people.

— Oct. 20, 2014: Militants unleash more attacks on Iraq's Shiite community, killing at least 33 people.

— Oct. 27, 2014: Two car bombings in Iraq, including one where a suicide attacker drove a Humvee into a checkpoint manned by Iraqi troops and pro-government Shiite militiamen, kill at least 38 people.

— Dec. 4, 2014: Car bomb attacks across Iraq kill at least 37 people.

— Feb. 8: Bombings in Baghdad kill more than three dozen people hours before the city's longtime curfew comes to an end.

— Feb. 11: Heavy clashes between security forces and militants in Baghdad and near Tikrit kill 34 people.

— May 9: Forty inmates in a prison in eastern Iraq, including some convicted of terrorism charges, escape amid a riot that kills at least six police officers and 30 prisoners.

— June 1: Three Islamic State suicide car bombers target a police base in Iraq's western Anbar province, killing at least 41 police officers and Shiite militiamen.

— July 17: An Islamic State-claimed truck bombing kills at least 115 people, including women and children, at a crowded marketplace in Iraq's eastern Diyala province. The mostly-Shiite victims were gathered to mark the end of the Islamic holy month of Ramadan.

— Aug. 10: An Islamic State suicide car bomber tears through a marketplace in Baquba, the provincial capital of Diyala, killing 35 people.

— Aug. 13: A massive truck bomb rips through a busy market in Baghdad's sprawling Shiite neighborhood of Sadr City, killing at least 62 people. Islamic State groups claims responsibility for the attack.