CROWDS of passengers were boarding buses to leave Baghdad for the more tranquil south when the first of three bombs exploded yesterday, ripping through the busy bus station in the centre of the capital.

Minutes later a second exploded, catching the injured from the first blast and the rescuers who came to their aid. Then, as the casualties were being rushed to nearby al-Kindi hospital, the third exploded just metres from the gates of the emergency room, cutting down policemen, doctors and the wounded.

The devastating series of bombs that hit Baghdad yesterday, killing at least 43, broke the recent tense lull that prevailed across the city in the run-up to the expected announcement of a new constitution. Insurgents were said to be stockpiling their explosives for a spectacular attack to greet the country’s new charter, but the deadline passed without agreement and it was only yesterday morning, when meetings resumed, that the explosions happened.

When they did, they were ingeniously barbaric, detonating over a period of less than 20 minutes. “This was organised — they were trying to kill as many people as possible,” Ali Jassim, a traffic policemen, raged amid the wreckage in al-Nahda bus station.

The terminal links the capital with the towns of the Shia south and many victims were believed to be Shias, the majority community so often targeted by a Sunni insurgency trying to ignite civil war.

Many had been boarding a bus going to Basra when the first explosion, a car bomb, ripped through the vehicle, incinerating it and killing most of those on board. Police said that it was unclear if that explosion had been caused by a suicide bomber. The next two appear to have been detonated by remote control.

Mr Jassim had been rushing to the scene of the first explosion to clear a path through the panicking crowd for ambul- ances when the second bomb exploded, wounding two of his colleagues. He rushed them to al-Kindi hospital and had reached the emergency room when the third went off. His colleagues died instantly.

One old man, with a group carrying a coffin, turned on the police. “All of you are cowards,” he shouted. “Why don’t you protect the people? Why are the Shia being killed? What have they done?” Others cursed the Iraqi Government and Prime Minister, blaming them for the carnage. A lone policeman sobbed as he looked at the bodies laid out in the courtyard.

Blaming the Government for Iraq’s unrest, rather than the Americans, has grown more common, a disturbing development for any who hope to govern this country. Washington is adamant that the passage of a constitution will undermine the insurgents, but similar projections have been made at every step of the political process so far without any let-up in the bloodshed.

The bombing was the first on this scale in Baghdad for nearly a month, and came hours before political leaders resumed their negotiations over the draft constitution. Weeks of deliberations have exposed the division between Sunnis, Shias and Kurds. The committee has until Monday to agree a text or risk the dissolution of parliament.

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