The guerrillas forced the bus to stop as it travelled in the Benhamdani area in Blida province at about 3am.
Algerian security forces said the 20 people were killed "in a cowardly way", a phrase used for attacks in which victims have their throats cut. Seven people were wounded in the raid. The latest attack brought to nearly 60 the number reported killed in Blida province in under a week. The provincial capital of the same name is just 30 miles south of Algiers.
Reuter - Paris