UNITED NATIONS -- The U.N. chief vowed Wednesday to keep United Nations staff in Algeria, saying the bombing of its offices in the north African nation will not deter the world body from helping people in need.

At least nine U.N. workers were among the 31 killed in the attack in Algiers by an affiliate of al-Qaida. U.N. deputy spokeswoman Marie Okabe said the situation on the ground is fluid and confusing, with some U.N. staffers still missing.

It was the worst attack against U.N. staff since an August 2003 bombing at U.N. headquarters in Baghdad killed the organization's top envoy in Iraq, Sergio Vieira de Mello, and 21 others.

Secretary-General Ban Ki-moon told the U.N. General Assembly in a live video address from Bali, Indonesia, where he is attending the U.N. conference on climate change, that the United Nations will remain in Algeria.

"Our mission has been, and will always be, to help those most in need," he said. "The Baghdad attack will not deter us. Neither will this most recent attack. Our colleagues in Algiers would ask no less."

Okabe said: "Essential staff are remaining in Algiers and will continue U.N. operations."

Former Secretary-General Kofi Annan pulled all U.N. international staff out of Iraq two months after the August 2003 bombing, which was followed by a second bombing at U.N. headquarters in Baghdad and a spate of attacks on humanitarian workers. He allowed a small U.N. contingent to return to Baghdad in August 2004 but the number has remained low since then because of security concerns.

Ban said he spoke to Algerian President Abdelaziz Bouteflika Wednesday evening and asked him to take all necessary measures to ensure the security of U.N. personnel.

The U.N. chief expressed "shock and outrage" at Tuesday's twin truck bombings that targeted U.N. offices and a government building.

"In Algiers, we have today one more ugly reminder that terrorism remains the scourge of our times," he said. "The international community must be resolute in opposing those who prey on the innocent and vulnerable and those, like the United Nations, who seek only to help them."

The U.N. said the nine staff confirmed dead included six Algerians, one Senegalese, one Dane and one Filipino.

Okabe told reporters the dead included staff from the International Labor Organizations, the U.N. refugee agency, the World Food Program, the U.N. Development Program, the U.N. Population Fund and the Department of Safety and Security.

Rescuers pulled two surviving U.N. employees from under the rubble on Tuesday, and both are now receiving medical treatment, Okabe said.

"Hopes for finding any more survivors in the rubble have dimmed and the local authorities have started to use heavy machinery to clear the site," she added.

U.N. officials on Tuesday had said at least 11 of the world body's staff members were killed. Okabe said the 11 dead was a preliminary figure and that officials are now counting only those who are confirmed dead and whose families have been notified.

Ban said he sent several of his top aides to Algiers, including UNDP administrator Kemal Dervis, to determine how best to aid victims and their families.

About 175 U.N. employees worked in Algeria, including about 115 locally based staff, Okabe said.

Before Tuesday, more than 250 U.N. civilian employees had been killed either by violence or in accidents since January 1992, when such record-keeping began, U.N. officials said. Those figures do not include the deaths of U.N. staff from peacekeeping missions.

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Associated Press Writer Carley Petesch contributed to this report from the United Nations.