At least six people have been injured by a car bomb suspected to be the work of Euskadi Ta Askatasun (Eta), the Basque separatist group.

The explosion was in front of a police station in Ondarroa, a northern Basque town, and was the second attack in the early hours of Sunday morning.

Six people - three policemen and three civilians - were lightly injured in the blast, the Basque interior ministry said.

A coded warning from Eta gave Spanish police time to clear the area.

The explosion was the second car bomb in the Basque region overnight. An earlier blast in the regional capital of Vitoria-Gasteiz caused no injuries but considerable damage.

The interior ministry has blamed Eta for both attacks.

Since abandoning a ceasefire in June 2007, Eta has killed four people and carried out a series of bombings mostly in the northeastern Basque region.