Police then shot and killed two suspected attackers who were following the lorry in another vehicle, the police said.

All of the dead officers belonged to a rapid-reaction unit of the military police, officials said.

Over the past year violence has escalated in the mountainous and forested terrain of Kabylia, where isolated fighter groups have aligned with al-Qaeda and staged a series of bombings.

Security forces killed seven men on Wednesday near the village of Toughrast, located at least 40km north of Kabylie's main town, Tizi Ouzou, a security official said.

Acting on a tip-off from two suspected members of a network that supports armed opposition groups in the region, security forces swooped as the group were preparing to buy supplies, the official said.

Security forces seized automatic weapons, ammunition, food and pharmaceuticals, the official said.

Such attacks in Algeria started in 1992 after the army cancelled the second round of the country's first-ever multiparty elections, stepping in to prevent likely victory by the Islamic Salvation Front, commonly known by its French acronym, FIS.

Armed opposition groups turned to force to overthrow the government, with up to 200,000 people killed in the violence that ensued.