A huge truck bomb struck at the heart of the international humanitarian effort in Iraq yesterday, destroying part of the United Nations headquarters in Baghdad and killing at least 16 people including the head of the UN mission.
Mr Sergio Vieira de Mello, the UN special representative, a respected Brazilian diplomat and the embodiment of the international community's post-war role, survived for at least three hours trapped under the rubble, but died of his injuries before rescue workers could reach him.
Iraqis and international workers were among the dead and more than 100 wounded. Many of the casualties were rushed to a local civilian hospital, while some were taken by helicopter to US military hospitals.
US officials described the bombing as a suicide attack directly targeted on Mr de Mello (55) who was in his office on the third floor when the truck exploded. One news agency reported that Mr de Mello was able to call for help on his mobile phone.
The bomb was hidden in a cement mixer lorry, but confusion surrounds whether it was allowed into the compound - where building work has been going on - or whether it was detonated while parked outside a new 12 feet perimeter wall.
"All this happened right below the window of Sergio Vieira de Mello," a UN spokesman, Mr Salim Lone, said. "I guess it was targeted for that. It was a pretty huge bomb. His office and those around it no longer exist, it's all rubble.
"I grieve most of all for the people of Iraq because he was really the man who could have helped bring about an end to the occupation. An end to the trauma the people of Iraq have suffered for so long."
Coming 11 days after a car-bomb at the Jordanian embassy, the attack confirmed a shift in tactics away from the American military to "soft" international targets in an apparent attempt to disrupt Iraq's reconstruction. It also left no doubt that the blue UN flag offers no protection.
The UN Security Council condemned the bombing, the worst attack against a UN civilian mission in its 58-year history, saying it had crossed a "red line".
But the council said it would not be deterred from continuing relief work, issuing a statement vowing: "Such terrorist incidents cannot break the will of the international community to further intensify its efforts to help the people of Iraq."
However those efforts will now be constrained by much more cautious security precautions for the UN's 600 foreign and roughly 2,500 Iraqi employees in Iraq. The bombing marks a serious setback for the US-led occupation, and the coalition's daily struggle to prevent Iraq sinking into chaos. "By their tactics and their targets these murderers reveal themselves once more as enemies of the civilised world," a sombre President George Bush told reporters at his Texas ranch.
With the death of Mr de Mello, the UN has lost its most experienced troubleshooter, a man who had been sent on many of the most sensitive and dangerous peace missions.