ALGIERS — Truck bombs exploded minutes apart today in central Algiers, heavily damaging U.N. offices and partly ripping the facade off a government building. At least 26 people were killed, including U.N. workers, and scores were wounded, officials said.

The North African branch of Al Qaeda claimed responsibility in a Web site posting and said suicide bombers carried out the attack. Jihadists in Iraq who later affiliated with Al Qaeda were blamed for attacking the U.N. headquarters in Baghdad in 2003, killing 22.

The two bombs exploded around 9:30 a.m., and one had deliberately targeted United Nations offices, according to the head of the U.N. refugee agency in Geneva. The other bomb struck outside Algeria’s Constitutional Council, Interior Minister Noureddine Yazid Zerhouni said.

Al Qaeda-linked militants who were arrested after deadly April bombings in Algeria had identified those buildings as among their future targets, the official APS news agency quoted him as saying.

A small tanker truck was used in the U.N. attack, while a van was used in the other bombing, he said.

A statement on a militant Web site said two “martyrs” of Al Qaeda in Islamic North Africa drove vehicles each loaded with more than 1,700 pounds of explosives “to attack the headquarters of the international infidels’ den” and the Algerian Constitutional Council.

“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.

The attacks killed 26 people, an Interior Ministry statement said, adding that the dead included two U.N. staffers — one Danish, the other Senegalese. Also among the dead were three people from Asia, although their nationalities were not given.

As many as 177 people were wounded.

A U.N. spokeswoman, Marie Okabe, said in New York that five U.N. employees were believed to be among the dead. A chief spokesman for the U.N. High Commissioner for Refugees in Geneva, Ron Redmond, said only two UNHCR staff members — both drivers from Algeria — were killed, and that more than a dozen workers were injured, one seriously. All missing employees were accounted for, he added.

Initial reports from hospital and rescue officials had put the death toll at 45.

The UNHCR chief, Antonio Guterres, “said he has no doubt that the U.N. was targeted,” according to Mr. Redmond. He added that “it is a very small street that just separates a U.N. compound, and it happened right there.”

Secretary-General Ban strongly condemned the bombings as a “cowardly strike” and ordered a review of security.

“This is just unacceptable,” a somber Ban, who was in Bali, Indonesia, said. “I would like to condemn it in the strongest terms. It cannot be justified in any circumstances.”

The Bush administration added its denunciation.

“We condemn this attack on the United Nations office by these enemies of humanity who attack the innocent. The United States stands with the people of Algeria, as well as the United Nations as they deal with this senseless violence,” a National Security Council spokesman, Gordon Johndroe, said.

“An attack like this is among the easiest actions to carry out. I have always said that we are not safe from these sorts of attacks,” he told reporters.

The U.N. Development Program building collapsed, and the refugee agency’s office across the street sustained damage, Ms. Okabe said. The development program building also housed other U.N. agencies, including the World Food Program, the International Labor Organization and the U.N. Population Fund, and employed 175 people, about 115 locally based staff, she said.

The soot-covered remains of parked cars mangled by the blast littered the street in the upscale Hydra neighborhood, which houses many embassies and has a substantial foreign population.

The bomb at the Constitutional Council, which rules on the constitutionality of laws and oversees elections, ripped chunks off the white facade of the new building, exposing the red brick underneath, and left a hip-deep crater in the road.

Some victims had been riding a school bus, the APS news agency said, and the remains of an orange bus were outside the Constitutional Council building.

Mohammed Faci, 23, told AP Television News that he was in a different bus that was jolted by the blast and he broke his arm.

“It was horror,” Mr. Faci said, describing the pandemonium following the explosion that gutted the other bus. “I’m glad I wasn’t in that first one.”

Osama bin Laden’s chief deputy, Ayman al-Zawahri, in September called for jihad in North Africa to “cleanse (it) of the children of France and Spain.”

Today’s date — December 11 — could point to an Islamic terrorism link. Al Qaeda has struck on the 11th in several countries, including the September 11, 2001, attacks in the America. Al Qaeda in Islamic North Africa claimed responsibility for attacks on April 11 that hit the Algerian prime minister’s office and a police station, killing 33 people.

December 11 has another meaning for Algerians. On that date in 1960, pro-independence demonstrations were held in Algeria against colonial ruler France. The Constitutional Council is located on December 11, 1960, Boulevard.

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 turned to force to overthrow the government, with up to 200,000 people killed in the ensuing violence.

The past year has seen a series of bombings against state targets, many of them suicide attacks.