Masked police officers inspect the scene of small bomb that exploded outside Spanish governmental industrial premises in Arrigorriaga, northern Spain, 01 May 2008

Spanish officials say three bombs have exploded in northern Spain's autonomous Basque region, without causing casualties.

The officials say two bombs exploded early this Thursday morning near a government building in the city of San Sebastian following a warning call from the Basque separatist group ETA.

A third bomb went off at around the same time in the neighboring town of Arrigorriaga without a warning.

ETA carried out several bomb blasts in Spain's Basque region last month, including one attack that wounded seven police officers in the city of Bilbao.

ETA has killed more than 800 people in four decades of fighting for an independent Basque state in northern Spain and southwestern France.

Spanish Prime Minister Jose Luis Rodriguez Zapatero has ruled out further talks with the group since it scrapped a cease-fire in June 2007.

Some information for this report was provided by AFP, AP and Reuters.