ALGIERS, Algeria -- Two truck bombs set off in quick succession sheared off the fronts of U.N. offices and a government building in Algeria's capital Tuesday, killing at least 26 people and wounding nearly 200 in an attack claimed by an affiliate of al-Qaida.

Al-Qaida in Islamic North Africa, in a posting on a militant Web site, called the U.N. offices "the headquarters of the international infidels' den." A U.N. official said at least 11 of its employees died.

The bombs exploded 10 minutes apart around 9:30 a.m., devastating the U.N. refugee agency and other U.N. offices along a street in the upscale Hydra neighborhood, as well as Algeria's Constitutional Council, which rules on the constitutionality of laws and oversees elections.

The blasts, which came on the month's 11th day, a number rich in symbolism both for Algerians and al-Qaida, drew swift international condemnation.

"It was horror," said Mohammed Faci, 23, whose arm was broken by the blast as he rode a bus.

The targeting of U.N. offices was a new development in the 15-year war between Algeria's secular government and Islamic insurgents, who previously focused their hate on symbols of the military-backed administration and civilians.

Al-Qaida's self-styled North African branch's Web posting said two suicide bombers attacked the buildings with trucks carrying 1,760 pounds of explosives each. Images were provided of the two "martyrs," identified as Ibrahim Abu Uthman and Abdul Rahman Abu Abdul Nasser Al-Aassemi.

"This is another successful conquest ... carried out by the Knights of the Faith with their blood in defense of the wounded Nation of Islam," said the statement, which claimed that more than 110 "Crusaders and apostates" were killed.

Interior Minister Noureddine Yazid Zerhouni said the Algerian government was "certain" that al-Qaida in Islamic North Africa -- formerly known as the Salafist Group for Call and Combat -- "was behind the attack."

Counterterrorism officials in Algeria's former colonial ruler, France, say the group is drawing members from across North Africa.

Although it is thought to have only several hundred fighters, the al-Qaida affiliate has resisted security sweeps to organize suicide bombings and other attacks as it shifts its focus from trying to topple the government to waging holy war and fighting Western interests.

Al-Qaida has been urging attacks on French and Spanish interests in North Africa. In September, Osama bin Laden's chief deputy, Ayman al-Zawahri, called for jihad in North Africa to "cleanse [it] of the children of France and Spain."

Al-Qaida has struck on the 11th in several countries, including the Sept. 11, 2001, attack in the U.S. Al-Qaida in Islamic North Africa claimed responsibility for attacks last April 11 that hit the Algerian prime minister's office and a police station, killing 33 people.

Dec. 11 itself has meaning for Algerians. On that date in 1960, pro-independence demonstrations were held against the French colonial rulers. The Constitutional Council is located on December 11, 1960 Boulevard.

Anne Giudicelli, a former French diplomat specializing in the Middle East who runs the Paris-based consulting firm Terrorisc, said Tuesday's attack bore the "clear signature" of al-Qaida-affiliated groups -- in the choice of targets and use of near simultaneous bombings.

"They attacked ... neighborhoods where there is plenty of security, which is a way to show their strength in the war with security services," she said.

Louis Caprioli, a former assistant director of France's DST counterintelligence agency who now works for the risk-management company Geos, said the attack may have been a reaction to the arrest last month of Bouderbala Fateh, a leading figure in Algeria's al-Qaida branch. The raid found three bombs, 1,760 pounds of explosives and a rocket launcher in the group's hide-out.

Algeria's militants "feel a need to fight back after many arrests, after (militants) turned themselves in or were killed," he said. "They needed to react to show their operational capacity."

After Tuesday's bombings, one damaged U.N. building stood with its insides spilling into a street littered with the soot-covered remains of parked cars crunched by the blast. The Constitutional Council lost chunks of its white facade, exposing red brick underneath, and a neck-deep crater was gouged in the road outside.

The attacks killed 26 people, an Interior Ministry statement said Tuesday evening. It said the dead included two U.N. staffers -- one Danish, the other Senegalese -- as well as three people from Asia whose nationalities were not given. Another 177 people were injured, of which 26 were hospitalized, the ministry said.

Other sources said the toll was higher. An official at the civil protection agency who spoke on condition of anonymity said 45 people were killed. A doctor at a hospital who said he was in contact with staff at other hospitals put the death toll at a minimum of 60.

Algerian Prime Minister Abdelaziz Belkhadem, quoted by the APS news agency, called the higher figures inflated and said the government had no reason to hide the real death toll.

"There are still a number of people unaccounted for, a number of people trapped under the rubble, and the latest death toll that we have is 11," U.N. deputy spokeswoman Marie Okabe said.

Marie Heuze, a spokeswoman for the world body in Geneva, said that if all the missing were dead, it would be the deadliest assault on the United Nations since the 2003 attack on U.N. offices in Iraq that killed top U.N. envoy Sergio Vieira de Mello and 21 others. That attack was staged by Islamic extremists who later affiliated with al-Qaida.

World leaders roundly condemned the attack. President Bush extended condolences for those killed in "this horrible bombing," National Security Council spokesman Gordon Johndroe said.

French Foreign Minister Bernard Kouchner condemned the attacks as "barbarity" and said that while Algeria had made great progress in fighting terrorism, "the sordid beast is not yet dead."

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 a likely victory by an Islamic fundamentalist party.

Islamist armed groups then resorted to force in trying to overthrow the government, and up to 200,000 people have been killed in the ensuing violence.