The killing of UN top official in Iraq, Sergio Vieira de Mello, and at least 15 staffers in Baghdad stunned the world body at its headquarters in New York on Tuesday.
The UN Security Council condemned the bombing as a "terrorist, criminal attack" while Secretary-General Kofi Annan cut short his vacation in Finland and called for the "perpetrators of this outrage" to be brought to justice.
At the UN headquarters in New York, the flags of all 191 membercountries were taken down, leaving only the blue-and-white UN flagflying at half mast.
Dazed staff wept as television displayed grim pictures of the devastation at the main UN office building in Iraq, where some 300of their colleagues worked. Many were still trapped in the rubblesand the death toll was certain to go up, officials said.
In a statement, Annan said De Mello's death was "a bitter blow for the United Nations and for me personally." "The death of any colleague is hard to bear but I could think of no one we could less spare," the UN chief said.
UN officials said they believe the office of De Mello, the UN Special Representative for Iraq, had been the target of the suicide truck bombing.
The bomb ripped through the Canal Hotel, which housed the UN headquarters in Iraq, killing at least 15 and injuring more than 100.
De Mello, 55, had already served with honor in Kosovo, East Timor and other hot spots around the world to handle difficult missions for the world body, before he was temporarily moved from his post as UN High Commissioner for Human Rights to become the UNSecretary-General's special representative in Iraq in June.
"He was working day and night to help the Iraqi people regain control of their own destiny and build a future of peace, justice and full independence," Annan said. "Let us strive to be worthy ofhim, and to complete the work that he began, so that his death will not have been in vain."
"Nothing can excuse this act of unprovoked and murderous violence against men and women who went to Iraq for one purpose only: to help the Iraqi people recover their independence and sovereignty, and to rebuild their country as fast as possible, under leaders of their own choosing," Annan added.
The 15-member Security Council affirmed that the blast would not deter the world body from its work of rebuilding Iraq. "Such terrorist incidents cannot break the will of the international community to further intensify its efforts to help the people of Iraq," council members said in a statement read by Deputy UN ambassador Fayssal Mekdad of Syria, the Security Council presidentfor August.
Annan's spokesman Fred Eckhard said the bombing inevitably raised the questions over the future of the UN Assistance Mission in Iraq, which was set up by the Security Council last week to coordinate humanitarian assistance and give political advice.
"Of course we will have to ask how safe we feel Iraq is as a place for the hundreds of UN staff members who were going to join Sergio's team as part of the new UN mission there," Eckhard said.