Funerals have begun in Baghdad for the 155 people so far known to have died in yesterday's massive car and truck bombings outside government buildings.

The death toll in the twin blasts rose overnight as eight more critically injured people succumbed to their wounds in hospital.

Iraqi security forces were on heightened alert this morning, with roads lined by Army humvees and new checkpoints springing up around the capital, causing traffic gridlock in the rush hour.

Streets just north of the fortified Green Zone remained closed as rescue workers dismantled debris and investigated, helped by US bomb disposal teams and forensics experts.

A truck carrying a tonne of explosives hidden below the seats exploded at a busy intersection near the Justice Ministry. Almost simultaneously, a car packed with 700kg of explosives went off opposite the nearby provincial government building. The force of the blasts left charred corpses and body parts strewn across the streets of the capital.

As in previous attacks, the bombs were targeted squarely at disrupting government services. On August 19, 95 people died in vehicle bombings on the Foreign Affairs and Finance Ministries, an attack blamed on Sunni insurgents from Saddam Hussein's outlawed Ba'ath party, based in neighbouring Syria.

Bombers have now killed or maimed more than 1,000 civil servants in the last few months.

This is likely to have an impact on parliamentary elections due to be held on January 16. Services such as health care and electricity are still well below what officials promised at the last elections.

"Sadness is overwhelming today in the office," said one government employee. She asked that her name not be used because she did not want to be reprimanded for speaking publicly about the authorities. "It's as if we are sitting at a funeral in the office because many of our colleagues and people we know were killed."

Many Iraqis are asking how the Government can protect them if it cannot protect itself. The explosives-laden vehicles were able to get into an area home to numerous government institutions and just hundreds of yards from the heavily fortified Green Zone where the US Embassy and the Prime Minister’s office are located.

Major General Qassim al-Mousawi, a spokesman for Baghdad's command centre, said that the vehicles appeared to have passed through several security check points to reach their targets.

Nouri al-Maliki, the Iraqi Prime Minister, vowed that the attacks would not derail the election as he toured the bomb sites yesterday. But other than stepping up the presence of police and army on the streets there is little that he can do in the short term to prevent further attacks.

President Obama rang Mr al-Maliki last night as he chaired an emergency meeting of the National Security Council to discuss the bombings with his police and military chiefs. The US President expressed his condolences, and urged Iraqi leaders to agree quickly on electoral reforms that are threatening to delay the election, according to one MP who took part in the discussions.

Washington fears that the electoral impasse could force American to keep troops in Iraq in numbers into next year, endangering the agreement that all US combat troops must withdraw by next August, and all US forces should be gone by the end of 2011.

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