The policemen were on guard outside a bank in the town of Medea on Tuesday, security officials said. The region around Medea is often targeted by the Armed Islamic Group (GIA) of Rashid Abu Tourab whose membership is believed to have dropped to about 30.
Tuesday's attack was the first of its kind by the GIA in several months.
Since the start of December at least 23 people, 16 armed Islamists and seven members of the security forces, have been killed in a violent campaign to create an Islamic state, according to a count by officials and the press. Nearly 880 people have died since January.
Calling off election
The unrest started after Algeria's armed forces called off a general election in January 1992 that the now outlawed Islamic Salvation Front (FIS) was poised to win.
The fighting has claimed at least 100,000 lives over the last
decade, according to an official toll, and more than 150,000
according to the press. Many of the victims have been civilians killed in massacres, bomb attacks and raids on isolated communities.