Emergency workers searched for bodies and survivors Wednesday after twin truck bombings by an affiliate of al-Qaida targeted U.N. offices and a government building in Algiers, killing at least 30 people.

Some estimates of the final death toll climbed well above the official Algerian government figures. Algerian Foreign Minister Mourad Medelci said on France's Europe-1 radio Wednesday morning that the official death toll was 30, up from 26 Tuesday night, after emergency workers spent the night hunting for victims beneath the remains of gutted buildings.

As many as 11 U.N. workers, possible more, were killed, U.N. officials said.

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The targeting of United Nations offices was a new development in Algeria's 15-year battle against Islamic insurgents, who previously focused on symbols of Algeria's military-backed government and civilians.

U.N. officials in Geneva said it was the worst single attack against United Nations staff and facilities since August 2003, when the global body's headquarters in Baghdad were hit by a truck laden with explosives. That attack killed 22 people, including the top U.N. envoy, Sergio Vieira de Mello, and was blamed on al-Qaida fighters in Iraq.

After Tuesday's attack in Algiers, U.N. Secretary-General Ban Ki-moon called for an immediate review of U.N. security in Algeria and elsewhere.

The sites of the blasts were cordoned off Wednesday by police, as emergency workers continued searching for victims or survivors and maintenance workers swept up soot and cleared out rubble.

The U.N. offices are in the upscale Hydra neighborhood of Algiers, which houses many foreign embassies and has a substantial foreign population. The U.S. and British embassies stepped up security. The French Embassy said that though violence had largely died down in recent years, "recent attacks show that it is time for a return to the most extreme prudence."

"The renewed threat by al-Qaida against French interests in North Africa cannot be ignored," the embassy said on its Web site.

Al-Qaida has called for attacks on French and Spanish interests in North Africa. French President Nicolas Sarkozy visited Algeria last week.

Al-Qaida's self-styled North African branch, in a posting on a militant Web site, said two suicide bombers attacked the buildings Tuesday with trucks carrying 800 kilograms (1,760 pounds) of explosives each.

It described the U.N. offices as "the headquarters of the international infidels' den." The other target, Algeria's Constitutional Council, rules on the constitutionality of laws and oversees elections.

Algerian Interior Minister Noureddine Yazid Zerhouni said the government was "certain" that al-Qaida's North Africa affiliate — formerly known as the Salafist Group for Call and Combat, or GSPC — "was behind the attack."

Militants arrested after previous bombings in April had identified the U.N. offices and the council building as future targets, Zerhouni said, according to the official APS news agency. A light tanker was used in the U.N. attack, and a light van in the other, he said.

Al-Qaida in Islamic North Africa is thought to have only several hundred fighters but has resisted Algerian security sweeps. Its members have rejected amnesty offers and have turned their sights from toppling the government to waging holy war and fighting Western interests.

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.