A U.N. spokeswoman told news agencies that four employees were killed after the blasts struck near a U.N. refugee agency building and inflicted heavy damage in an affluent Algiers neighborhood where several foreign embassies are located.
"We are looking through the rubble for people," said Jean Fabre of the U.N. Development Program in Geneva, after speaking with Marc Destanne De Bernis, the agency's top official in the Algerian capital, the Associated Press reported.
Algeria's interior minister says at least 22 people were killed in the blasts. Death tolls varied widely in the aftermath of the bombings. A health ministry source put the number of dead at 67, Reuters reported.
Interior Minister Noureddine Yazid Zerhouni said the Salafist Group for Preaching and Combat, the former name of al-Qaida's North Africa wing, is responsible for the bombings.
"We are sure that the GSPC is behind it," Zerhouni told a news conference.
"I have no doubt that the U.N. was targeted," said U.N. High Commissioner for Refugees Antonio Guterres on BBC World television.
The 11th has become a day of choice for major Islamist terrorist attacks, beginning with New York on Sept. 11, 2001, followed by Djerba, Tunisia on April 11, 2002, Madrid, Spain on March 11, 2004, and the attack on April 11 this year that killed 33 people in Algiers, the New York Times reported.
U.N. Secretary-General Ban Ki-moon strongly condemned the bombings.
"This is just unacceptable," said Ban, who was in Indonesia for a U.N. climate conference. "I would like to condemn it in the strongest terms. It cannot be justified in any circumstances."
Algeria has been battling Islamic insurgents since the early 1990s, when the army canceled the second round of the country's first multiparty elections, stepping in to prevent likely victory by an Islamic fundamentalist party. Islamist armed groups then tried to overthrow the government, with up to 200,000 people killed in the ensuing violence.
The last year has seen a series of bombings against state targets, many of them suicide attacks.