A bomb exploded today at around 6 am outside an office of the ruling Socialist party in Spain's northern city of Bilbao, the largest Basque city, injuring seven police officers.

City officials have blamed the attack on the Basque separatist group ETA.

Apparently the explosion was announced earlier this morning through a telephone warning. Police reported a suspicious package near the building and at the time of the explosion they had already finished evacuating the area. Luckily, the officers present at the scene were treated for minor injuries and none of them required hospital visits.

Even though there were no victims, the explosion was very powerful, causing a great deal of damage to the building. The Basque regional government interior minister, Javier Balza was quoted by CNN saying "It was an authentic bomb."

ETA has been responsible for the death of more than 825 people since the 1960s. Its mission regards an independent Basque country in northern Spain and southwestern France. The group was also blamed for the fatal shooting of a former town councilman from the Socialist Party, on March 7, two days before Socialist Prime Minister Jose Luis Rodriguez Zapatero won re-election.

ETA attempted a cease-fire in March 2006 in an effort made by authorities to end violence. Unfortunately, the bombing at Madrid’s airport in December 2006, which killed two men, put an end to the peace process.

The group officially terminated the cease-fire in June 2007, and has been blamed for three killings since then: two undercover Civil Guards shot in France and the shooting of the former town councilman.