Suspected members of the militant Basque separatist group ETA planted a bomb in the northern Spanish city of Bilbao early Thursday, causing slight injuries to seven police officers, sources at the Interior Ministry said, according to dpa. The bomb caused major damage to an office of the Basque branch of Spanish Prime Minister Jose Luis Rodriguez Zapatero's Socialist Party. It also damaged nearby buildings, parked vehicles and a water pipe, cutting water supplies in the area. One of the police officers was thrown down by the force of the blast. Others were hit by flying glass shards or suffered ear pain. Patrolling police officers spotted the bomb at 5 am (0300 GMT) and evacuated the area. A caller speaking in the name of ETA then warned a road rescue service that a bomb was about to go off. ETA has killed more than 820 people over four decades, three of them since it ended a ceasefire in 2007. The fight against ETA is one of the priorities of Zapatero's new government, which began work this week after the elections in March. ETA campaigns for a sovereign Basque state carved out of northern Spain and southern France.