Baghdad , Iraq -LRB- CNN -RRB- -- At least 30 Iraqi children riding in a bus were among the 160 people killed in Sunday 's twin car bombings in Baghdad , the Interior Ministry said Monday . At least 540 people were wounded in Sunday 's attacks , the deadliest in the capital in more than two years , the ministry said . One of the bombs exploded outside Baghdad 's governorate building , the other outside the Justice Ministry . The bombs detonated in quick succession about 10:30 a.m. , officials said . The children were packed in a mini bus that was outside the Justice Ministry building , a ministry official said . The vehicle carrying the explosives that detonated outside the ministry building was a stolen white pick-up from Falluja , Baghdad Gov. Salah Abdul Razzaq told CNN during his inspection of the bomb site . Images from the time of the attack showed the truck , linked to the Department of Water , pull up to the side of the building and blow up , he said . Plumes of smoke billowed from the sites as victims fled , some with blood streaming down their faces . The streets were strewn with debris , including charred cars and chunks of concrete . Some government buildings and others in the area were heavily damaged . Among the wounded were three American security contractors , the U.S. Embassy said , declining to provide further details . The area struck is close to the heavily guarded `` Green Zone , '' which houses the embassy . The blasts sparked questions about Iraq 's security and national elections planned for January . Iraqi Prime Minister Nuri al-Maliki , who visited the scene shortly after the explosions , said holding the elections as scheduled would send a strong message to the attackers . `` The cowardly attack ... should not affect the determination of the Iraqi people from continuing their battle against the deposed regime and the gangs of criminal Baath party , and the terrorist al Qaeda organization , ' '' al-Maliki said in a written statement . U.S. President Barack Obama called the attacks an attempt to derail progress in Iraq , and pledged to work closely with the country as it prepares for elections . Obama spoke with the prime minister and President Jalal Talabani to express his condolences and reiterate U.S. support . In August , more than 100 people were killed in a series of bombings that led to tightened security in Baghdad . Blast walls were installed across the city and checkpoints were added . Two years earlier , three truck bombings killed hundreds in Qahtaniya , in northern Iraq . Sunday 's attacks were the deadliest on Iraqi civilians since those blasts in August 2007 . A day before Sunday 's explosions , the U.S. ambassador to the United Nations , Susan Rice , visited Iraq for the first time . During her trip , she made a condolence stop at the Foreign Ministry , one of six sites attacked in August . Iraqis are supposed to go to the polls January 16 , but parliament has not passed key election legislation , putting the balloting in limbo . The president , prime minister and other top officials are scheduled to meet Monday to discuss the elections law and security concerns . CNN 's Jomana Karadsheh , Mohammed Jamjoom , and Mohammed Tawfeeq contributed to this report .