An Al-Qaeda-linked group claimed a brazen attack near Baghdad's heavily fortified Green Zone as a study published on Sunday said at least 112,000 civilians were killed during the decade-long conflict.
Ahead of the anniversary of the US-led invasion that ousted Saddam Hussein, the latest reports raise fresh questions about the capabilities of the security forces to prevent attacks such as the March 14 assault on the justice ministry claimed by the Islamic State of Iraq (ISI).
The attack involved a series of mid-day bombings in central Baghdad's Allawi neighbourhood, adjacent to the Green Zone which is home to several government buildings as well as the American and British embassies.
As the blasts went off, militants stormed the nearby ministry complex, clashing with security forces.
Accounts differed as to the success of the attack, but one official said two insurgents managed to detonate suicide vests inside the ministry building.
Overall, 18 people were killed and more than 30 wounded, security and medical officials said. But the ISI claimed to have killed 60 people, according to a statement distributed by the SITE monitoring service on Sunday.
Britain-based Iraq Body Count (IBC), meanwhile, published a study which concluded that at least 112,000 civilians were killed in the 10 years since the invasion of Iraq.
It said that, including combatants on all sides of the decade-long conflict as well as yet undocumented fatalities, the figure could rise as high as 174,000.
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"This conflict is not yet history," it said in its report, which put the number of civilian deaths since March 20, 2003 at between 112,017 and 122,438.
"It remains entrenched and pervasive, with a clear beginning but no foreseeable end, and very much a part of the present in Iraq."
IBC said that, over the years, Baghdad had been, and still is, the deadliest region, accounting for 48 percent of all deaths, while the conflict was bloodiest between 2006 and 2008.
It noted that violence remains high, with annual civilian deaths of between four and five thousand roughly equivalent to the total number of coalition forces killed from 2003 up to the US military withdrawal in December 2011, at 4,804.
In addition to Baghdad, the most violent regions were the northern and western provinces, dominated by the Sunni Arab minority which controlled Iraq during Saddam's rule but which has since been replaced by the Shiite majority.
The IBC report comes after a separate study published in British medical journal The Lancet said that at least 116,000 Iraqi civilians had died in Iraq between 2003 and the 2011 American withdrawal.
The researchers behind the Lancet study pegged the total financial cost of the war for Washington at $810 billion (625 billion euros), warning that it could eventually reach $3 trillion.
Iraq's military and police are persistently described by Iraqi and American officials as capable of maintaining internal security, but are unable to protect the country's borders, airspace and maritime territory.
But attacks such as the March 14 assault remain common, in addition to a vast array of shootings and bombings nationwide, killing hundreds of people on a monthly basis.
In February, 220 people died in attacks nationwide, according to an AFP tally based on reports from security and medical officials.