At least 95 people have been killed and over 560 wounded in a series of bomb and mortar attacks near high-profile targets in central Baghdad.
Two large truck bombings, four car bombs and a series of mortar attacks struck near government ministries and other sensitive targets in quick succession.
The Iraqi Foreign Ministry, Finance Ministry, parliament building and heavily guarded Green Zone diplomatic complex all sustained damage in the blasts.
One of the biggest explosions occurred near the Foreign Ministry in a residential area close to the Green Zone, killing dozens within the building.
The ministry said the truck that exploded, in what it said was a suicide attack, had been carrying 1.5 tonnes of explosives and ball bearings 'to cause maximum casualties.'
The blast flattened part of a wall surrounding the ministry and damaged the parliament building.
Just minutes before that attack, another truck bomb had exploded outside the Finance Ministry in the Waziriya district, destroying parts of a nearby bridge and badly damaging the building's facade.
In subsequent attacks, UN security guards said two mortar rounds landed inside the UN compound, also in the Green Zone.
Mortars also struck the Salhiya district of central Baghdad, home to army bases and the offices of a national television station.
Baghdad's security spokesman made a rare admission of culpability after the attacks.
'This operation shows negligence, and is considered a security breach for which Iraqi forces must take most of the blame,' Major General Qassim al-Moussawi told Iraqiya state TV.
UN Secretary General Ban Ki-moon said he was saddened by 'appalling' attacks.
The attacks were carried out on the six-year anniversary of a truck bombing on the UN compound in Baghdad in 2003, which killed UN special envoy Sergio Vieira de Mello and 21 other people.
The Baghdad government said this month most of the city's blast walls would be removed within 40 days, a sign of confidence in its security forces ahead of national elections due in January.
However, today's violence has undermined confidence in the government's ability to ensure security, on which Prime Minister Nuri al-Maliki has staked his reputation.
In a statement, Mr Maliki called for a review of security plans, but added that the attacks were aimed at 'raising doubts about our armed forces, which have proven themselves very capable of confronting terrorists'.
Such coordinated large-scale explosions near heavily guarded state buildings in Iraq are relatively rare.
Mostly Shia venues such as mosques have been targeted by bombings in the past two months in the capital and northern Iraq, where insurgents such as al-Qaeda have exploited disputes between the region's Kurds and Arabs.
