Al Qaeda in Islamic North Africa took credit Thursday for a homicide bomb attack east of the Algerian capital that killed four police officers in an announcement that appeared on militant Web sites.

A vehicle rigged with explosives slammed into the Naciria police station Wednesday, killing at least four officers and at injuring 20 others, according to the Algerian Interior Ministry.

"With the grace and guidance of God, he surprised the apostates and destroyed the entire headquarters over their heads, leaving behind dozens of dead and injured among the police," read the statement, which featured the name and picture of the one who carried out the attack.

The blast on Wednesday followed twin homicide bombings on Dec. 11 at U.N. offices and a government building that killed at least 37 people in the capital of Algiers.

The statement warned that were still "lines of martyrdom lovers" waiting to take part in new attacks and called on security forces to "lay down their arms and remove themselves from the fight against the mujahideen."

The attack, carried out by Abdullah al-Shaayani, was justified on the grounds that security forces "torture Muslim youth and shove them into dark prisons while waging war on jihad and the Mujahideen on behalf of their masters in the Elysee Palace and the White House," according to the statement.

Al-Arabiya briefly carried an unconfirmed Al Qaeda claim of responsibility Wednesday, but eventually dropped the report.

Security forces have been on maximum alert since earlier this week, after three trucks were stolen in the Algiers region, the newspaper Liberte reported Wednesday. The vehicles included a fuel tanker, and officials fear they might be used in homicide attacks, the report said.

Al Qaeda in Islamic North Africa emerged from an alliance between Usama bin Laden's international terrorist network and an Algerian Islamist movement known as the Salafist Group for Call and Combat.

The homicide bombings in December and others in April also were claimed by the same group, which has increasing used vehicles packed with explosives to deliver its strikes.

In July, a homicide bomber blew up a truck inside a military barracks southeast of Algiers, killing 10 soldiers. Two months later, at least 28 people died after an explosives-packed vehicle rammed into a coast guard barracks in the northern town of Dellys.

Algeria's Islamic insurgency broke out in the early 1990s, when the army canceled the second round of the country's first multiparty elections to prevent likely victory by an Islamic fundamentalist party. Armed groups then turned to force to overthrow the government, and up to 200,000 people were killed in the ensuing violence.

Until recently, the insurgency had been dyeing down, with militants' ranks dwindling after military crackdowns and amnesty offers. But in late 2006, the main Algerian militant group allied with Al Qaeda and began to wage larger-scale bombings and target foreigners — signs that Islamic fighters were regrouping.