Family members of a victim killed in one of two suicide bombings Sunday grieve at his funeral in Baghdad on Monday. At least 155 people died and about 500 were wounded when two bombs went off near government buildings. (Karim Kadim/Associated Press) Iraqi security forces reinforced checkpoints and guarded government buildings Monday, the day after two suicide bombings in the heart of Baghdad killed more than 150 people, the worst attacks in the country in more than two years.

Officials raised the death toll from Sunday's blasts to 155, including 24 children on a bus leaving a daycare near the Justice Ministry.

Officials said the explosions of two vehicles also wounded about 500 people, and warned that intelligence suggests other government buildings might be targets of future attacks.

The blasts, near the city's heavily fortified Green Zone administrative district, cast doubt on the ability of the government to ensure the safety of its citizens, and raised fears that such mayhem will only increase as Iraq prepares for crucial elections in January.

"This explosion made people furious," said Ahmed Hassan, an employee at the Ministry of Education. "People will not re-elect this government."

"Today, we came to work despite the fear inside us," said Siham Abdul-Karim, an employee of the Culture Ministry located near the site of the bombings and surrounded by police checkpoints on Monday. "We all wonder how could car bombs reach these institutions."

Attackers aim to 'spread chaos,' PM says

The attacks occurred just hours before Iraq's top leadership was scheduled to meet with heads of political parties to seek a compromise on election guidelines for the January vote.

Iraqi Prime Minister Nouri al-Maliki blamed the bombings on al-Qaeda and loyalists of former dictator Saddam Hussein, who he said want to "spread chaos in the country, undermine the political process and prevent the holding of parliamentary elections."

No groups have claimed responsibility for the blasts.

Smoke rises near the Iraqi Ministry of Justice, shortly after Sunday's blast in Baghdad. It was the bloodiest attack in the capital in over two years. (Reuters)

Investigators were attempting to piece together how two vehicles packed with explosives were able to pass through security checkpoints on the way to two government buildings, the Baghdad Provincial Administration building and the Justice Ministry.

Maj.-Gen. Qassim al-Mousawi, a spokesman for the city's operations command centre, said the first vehicle, a 26-seat bus, was carrying 1,000 kilograms of explosives, while the second vehicle, a minibus which blew up near the Baghdad Provincial Administration building, was carrying 700 kilograms of explosives.

Interior Minister Jawad al-Bolani said 76 people have been arrested so far, but did not provide information on who they were or how they were believed to be connected to the bombings.

The bombings were the deadliest attacks in the country since a series of massive truck bombs killed 500 villagers in northern Iraq in August 2007.

Sunday's death toll was the worst in Baghdad since April 2007, when a series of suicide bombings against Shia neighbourhoods killed 183.

Also on Monday, Iraqi security officials said a car bomb at a police checkpoint near the city of Karbala in southern Iraq killed at least four people.

With files from The Associated Press