In strikes that officials said were meant to disrupt national elections scheduled for May 17, Al Qaida claimed responsibility for bombing the Algerian prime minister's office as well as the barracks of an elite security unit. The car bombings on Wednesday killed at least 33 people and injured about 220 in the bloodiest strikes in the North African country in at least a decade.

"This is a crime, a cowardly act," Prime Minister Abdul Aziz Belkhadem, who was unhurt, said. "The objective was a media provocation shortly before the election."

Hours later, the Al Qaida Organization in the Islamic Maghreb claimed responsibility for the attacks, the latest in a series of bombings around the capital in 2007. An Al Qaida-aligned website displayed the photographs of three suicide car bombers, identifying them as Muadh Bin Jabal, Al Zubair Abu Sajda and Abu Dajana.

The official Algerian Press Service reported that at least nine people were killed in the suicide bombing at the prime minister's office. APS said another eight people were killed in the attack on the police special forces unit in the Bab Ezzouar suburb, 15 kilometers east of the capital. On Thursday, the agency upped the death toll to 33.

Officials said the Al Qaida campaign underlined the failure of an Algerian amnesty to quell the Islamic insurgency. They said about 300 of the estimated 900 members of the Salafist Brigade for Combat and Call, the predecessor of Al Qaida, had accepted the amnesty offer and surrendered to authorities.

"The Algerian people stretched out a hand to them, and they respond with a terrorist act," Belkhadem said.

A third car full of explosives was found in front of the offices of Interpol in Algiers. But security forces neutralized the bomb, said to contain 500 kilograms of explosives.

The U.S. embassy warned Americans of additional attacks in Algiers. The embassy said it ordered staffers to restrict their movement over the weekend.

Al Qaida, said to have deployed agents in neighboring Mauritania, Morocco and Tunisia, has also been targeting Algeria's energy sector. Over the last four months, Islamic insurgents have bombed two buses of expatriate workers employed in Algeria's natural gas industry.

Algerian security sources said the Al Qaida campaign did not come as a surprise. The sources said the merger of Al Qaida with the Salafist Brigade for Combat and Call in 2006 resulted in a significant increase in the capability of the Islamic insurgency, where operatives were sent for training in Iraq.

In its statement, Al Qaida, which claimed 45 dead, said attackers targeted the government headquarters in Algiers, Algeria's special forces and Interpol. The attacks were said to have comprised of truck bombs of 700 and 500 kilograms.

"We won't rest until every inch of Islamic land is liberated from foreign forces," an unidentified Al Qaida spokesman said in a recording broadcast by the Qatari-based A-Jazeera satellite television channel.