The Basque separatist guerilla group ETA says it was responsible for the killing of a policeman in the northern Spanish province of Navara.

The group said in a statement it planted the bomb that exploded outside the town of San Sebastian as police tried to take down a pro-ETA flag on Tuesday.

The attack prompted protests from tens of thousands of people in the northern town of Pamplona on Saturday.

ETA also said it considered Spain's governing right-wing party and the socialist opposition to be military targets because of their efforts to ban the pro-independence Basque party, Batasuna - alleged to be ETA's political wing.

A new law which seeks to ban political groups backing extremist violence won overwhelming support in the Spanish parliament last month.

From the newsroom of the BBC World Service