UNITED NATIONS - U.N. Secretary General Ban Ki-moon promised a review of security for U.N. operations around the world on Wednesday after car bombs claimed by al Qaeda killed at least 11 U.N. employees in Algeria.

The U.N. staff were among dozens killed in Tuesday's twin car bombs at U.N. buildings and a government building. Al Qaeda's North African wing claimed responsibility for the bombs targeting what it called "the slaves of America and France."

Ban addressed the U.N. General Assembly by videolink from Bali, in Indonesia, where he is attending a conference on climate change. He said the bombs were "a despicable strike against individuals serving humanity's highest ideals under the U.N. banner," and "an attack on all of us."

Ban said he had sent Kemal Dervis, the head of the United Nations Development Program which lost a number of staff, to Algeria to oversee support for victims and their families.

"The security and welfare of U.N. staff is paramount," Ban said. "We will take every measure to ensure their safety, in Algeria and elsewhere, beginning with an immediate review of our security precautions and policies."

Ban said the world body had enhanced security since a bomb that destroyed the U.N. office in Baghdad in 2003 and killed 22 people, including mission chief Sergio Vieira de Mello.

"Our brave men and women continue their difficult and dangerous work," he said.

"The Baghdad attack will not deter us. Neither will this most recent attack," he said, addressing the General Assembly after it stood for a minute's silence for the victims.

The U.N. staff union called on Tuesday for a full investigation "to determine if adequate security measures were in place to prevent such a horrifying act."

Authorities were still searching for survivors on Wednesday. Algerian Foreign Minister Mourad Medelci told Europe 1 television the official death toll was 30, while a Health Ministry source on Tuesday said 67 people were killed.