US President Barack Obama has led international condemnation of Sunday's double suicide bomb attack in Baghdad that killed at least 132 people.
Mr Obama branded the attacks - the worst in more than two years in Iraq - "hateful and destructive".
UK Foreign Secretary David Miliband said they were a "terrible reminder of the threat from violent extremism".
The blasts hit the ministry of justice and a provincial government office near the heavily fortified Green Zone.
Gabriel Gatehouse, BBC News, Baghdad
Sunday's blasts present a problem for President Barack Obama. He wants all combat troops out of Iraq by the end of August, in preparation for a full military withdrawal by 2012.
If the security situation deteriorates, the US military may have to revise this timetable. They will be asking searching questions about Iraq's security forces - are they competent and well enough trained to secure the country and are they immune from infiltration by insurgents?
After Sunday's attacks there will be those who will argue that the answer to both these questions is no.
More than 520 people were also injured when the two car bombs exploded in quick succession at 1030 (0730 GMT) as people headed to work during the rush hour.
The White House said President Obama had spoken to Iraqi PM Nouri Maliki and President Jalal Talabani to pledge his support.
Mr Obama said in a statement: "I strongly condemn these outrageous attacks on the Iraqi people, and send my deepest condolences to those who have lost loved ones.
"These bombings serve no purpose other than the murder of innocent men, women and children, and they only reveal the hateful and destructive agenda of those who would deny the Iraqi people the future that they deserve."
The International Zone, or Green Zone, is the administrative heart of the capital.
The Iraqi authorities said the suicide bombers drove their vehicles into parking bays and detonated them.
Traffic limits in the street were eased six months ago and blast walls repositioned as part of a programme which Mr Maliki said showed progress was being made against insurgents.
Dozens of the dead were said to be staff members of the ministry of justice and Baghdad provincial government.
Mobile footage captures blast in the Iraqi capital
No-one has yet said they carried out the attack.
The BBC's Gabriel Gatehouse in Baghdad says that hours after the explosions, rescue workers were still sifting through the rubble and the wreckage, looking for bodies and survivors.
DEADLIEST ATTACKS SINCE 2003
Aug 2007: More than 500 killed in attacks on villages near Sinjar
Jul 2007: 150 killed in truck bombing in Tuz Khurmato
Apr 2007: 191 killed in car bombings in Baghdad
Mar 2007: 152 killed in truck bombing in Tal Afar
Feb 2007: 135 killed in truck bombing in Baghdad
Nov 2006: 202 killed in multiple blasts in Baghdad
Mar 2004: 171 killed in bombings in Baghdad and Karbala
Hospitals struggled to deal with the wounded as ambulances brought in more and more casualties.
After Mr Maliki visited the scene he blamed al-Qaeda and supporters of former president Saddam Hussein.
"These cowardly terrorist attacks must not affect the determination of the Iraqi people to continue their struggle against the remnants of the dismantled regime and al-Qaeda terrorists," he said.
Overall, violence has dropped dramatically in Iraq compared to a year ago, although sporadic attacks still continue in several parts of the country.
But our correspondent says there are fears that violence may increase as the country heads towards parliamentary elections scheduled for the beginning of next year.
The bombs went off as senior politicians were meeting in central Baghdad to try to break the deadlock over a draft law that would enable elections to take place in January.
The meeting ended without agreement, but will re-convene on Monday.
Last week the Iraqi parliament failed to meet a deadline to pass the legislation because of differences on a number of issues, among them whether to tell voters which candidates are on the party lists.
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