Wednesday's killing took to nearly 40 the number of people killed in the past 10 days and marked an increase in the activities of armed Islamists after weeks of relative lull.
Security sources said a "terrorist group" ambushed two police vehicles outside the village of Beni Douala in Tizi-Ouzou province, just east of the capital Algiers.
Security forces immediately cordoned off the whole area in pursuit of the attackers, it said.
Earlier, Algerian security sources accused armed Islamists of killing 12 people overnight Tuesday in western Algeria.
The sources said the 12 were "assassinated” on a road near Boumedefaa, in Ain Defla province. Two other people were injured during the attack.
The victims were stopped at a fake checkpoint some 160 km west of Algiers. They were then shot. No other details were available.
Boumedefaa is a region where armed Islamists are known to be active.
Last week 14 members of one family were killed in an attack in the Chlef region, 200 km west of the capital.
Since the beginning of May more than 100 people have been killed in attacks blamed on Islamist opponents of the regime, taking the toll this year to nearly 520.
The Islamists have been waging a war against the government during the last decade in their aim to create an Islamic state in this north African country.
Between 100,000 and 150,000 Algerians have been killed in violence that erupted in 1992 after the military-backed government cancelled parliamentary elections that Muslim parties were poised to win.
Most Islamist groups have laid down their weapons but the Armed Islamic Group (GIA) continues to hold out away from the urban centres. It has been accused of carrying out many massacres in the 13-year-old conflict as have pro-government forces and militias.
The renewed killing comes as the country grapples with the aftermath of a massive earthquake that has killed 2,300 people and injured more than 10,000.