At least 147 people died Sunday after two car bombs detonated in Baghdad, targeting two Iraqi government buildings.
With casualty figures still rising, officials said that nearly 600 people had been injured and taken to six area hospitals.
So many people were wounded that even civilian cars were pressed into service to ferry casualties to area hospitals, said a Baghdad hospital official who spoke to The Associated Press on condition of anonymity.
The two vehicles were packed with explosives and detonated less than a minute apart in the centre of the Iraqi capital. They targeted the Justice Ministry and the Baghdad provincial administration, officials said.
The attack raised fears that such mayhem will only increase as Iraq prepares for crucial January elections.
"These bombings serve no purpose other than the murder of innocent men, women and children," U.S. President Barack Obama said in a statement.
He went on to say that the bombings "only reveal the hateful and destructive agenda of those who would deny the Iraqi people the future that they deserve."
Ali al-Dabbagh, an Iraqi government spokesman, told the BBC he suspected that al-Qaeda militants were responsible for the bombings. It was not clear whether the attacks had been carried out by suicide bombers.
The attacks happened near the city's heavily fortified Green Zone administrative district.
The attacks occurred just hours before Iraq's top leadership was scheduled to meet with heads of political parties in order to reach a compromise on election guidelines needed to hold the January vote.
At least 25 staff members of the Baghdad Provincial Council, which runs the city, and 35 employees of the Ministry of Justice were killed in the bombing, police and medical authorities said.