BAGHDAD: Grappling with a spike in violence and a worsening political situation, Iraq on Wednesday marked 10 years since a US-led invasion that sought to establish a stable, democratic ally in the Middle East.

The event was met with little fanfare in Baghdad, though, a day after a wave of bombings and gun attacks killed 56 people across the country, as some ministers began a cabinet boycott and officials delayed provincial polls.

Al-Qaeda front group the Islamic State of Iraq (ISI) claimed responsibility for the violence in statements posted on jihadist forums, while another car bomb in east Baghdad on Wednesday killed two people.

In Washington, US President Barack Obama had released a muted statement the day before that paid tribute to the "sacrifice" of his nation's troops, but had few words for the Iraqi people, promising instead to support wounded American veterans of the conflict.

Iraqi officials have not announced any ceremonies to mark the invasion anniversary, with events more likely to be held on April 9, the day Baghdad fell, and there was little reference to the invasion across the capital on Wednesday.

"It was a dream to get rid of Saddam -- this was a positive thing they did -- but what came after is all negatives," said Raad Mohammed, a 51-year-old portrait photographer in central Baghdad's Tahrir Square.

"Now, everyone is living through tragedies, and nothing was accomplished in these past 10 years."

Nearby, however, Sabah Shawki noted that while violence had been terrible, and the country's basic services were a shambles, the invasion had brought him much-needed religious freedom.

"Now, I can pray to my God," the 34-year-old resident of the sprawling Shiite neighbourhood of Sadr City said. "In Saddam's time, I could only pray to the God he said I could pray to."

Violence has spiked ahead of the anniversary, with 120 people killed in the past week, according to an AFP tally based on reports from security and medical officials, with the worst of the violence striking on Tuesday.

In all, at least 20 explosions and multiple shootings left 56 people dead and more than 220 wounded on Tuesday, Iraq's deadliest day in six months, reflecting the brutal unrest that continues to plague the country.

An average of 10 people died in attacks each day so far this month, according to AFP's figures.

Launched a decade ago with the stated goal of wiping out Saddam's stores of weapons of mass destruction, which were never found, the focus of the divisive war quickly shifted to solidifying Iraq as a Western ally in an unstable region.

Though the war itself was relatively brief -- it began on March 20, 2003, Baghdad fell weeks later, and then-US president George W. Bush infamously declared the mission accomplished on May 1 -- its aftermath was violent and bloody.

Separate reports by Britain-based Iraq Body Count and researchers at The Lancet put the overall death toll from the decade of bloodshed at more than 112,000 civilians.

The fatalities peaked in 2006 and 2007, when thousands were being killed on a monthly basis, with the violence only being brought under some semblance of control from 2008 onwards, as the American troop "surge" coincided with Sunni tribal militias deciding to side with US forces.

But political reconciliation, the strategic goal of the surge, was never fully achieved.

From territorial disputes in the north to questions over the apportioning of the country's vast energy revenues, a number of high-level problems remain unresolved, and Prime Minister Nuri al-Maliki has locked horns with his erstwhile government partners essentially non-stop for months.

On Tuesday, powerful Shiite cleric Moqtada al-Sadr suspended his bloc's participation in sessions of Iraq's national unity cabinet in response to Maliki challenging parliamentary decisions in court.

It means five ministers loyal to the Sadrist movement will not attend weekly cabinet meetings until further notice.

Authorities, meanwhile, announced provincial polls scheduled for April 20, Iraq's first vote in three years, would be delayed in Anbar and Nineveh provinces, citing security concerns including threats to candidates.