MADRID, Spain (CNN) -- A bomb has exploded at a political party office in northern Spain early Friday, causing damage but no injuries -- just 10 days ahead of national elections.
Police inspect the damage caused by a bomb at the Basque Socialist party offices in Derio.
Authorities blamed the blast on the Basque separatist group ETA.
A police spokesman told CNN that authorities received a warning call in the name of ETA shortly after midnight Friday about a bomb in the doorway of the ruling Socialist party office in the Basque town of Derio.
Police rushed in to evacuate sleeping residents from their homes.
The blast, which occurred around 1 a.m. local time (0000 GMT), damaged various buildings.
Last week Spain ordered its security forces to go on maximum alert ahead of March 9 general elections.
Sources said a key concern has been potential attacks by ETA, which is blamed for more than 800 deaths in its long fight for Basque independence.
Under a maximum alert, police will be backed by the armed forces in patrolling transport hubs, shopping areas, sporting events, landmark buildings, the headquarters of political parties and their campaign events, as well as other potential terrorist targets, the government said.
The Madrid train bombings, blamed on Islamic terrorists, came just three days before the 2004 elections, killing 191 people and wounding more than 1,800.
Socialist Prime Minister Jose Luis Rodriguez Zapatero won an unexpected, upset victory over the conservative candidate, Mariano Rajoy, after the train bombings.
The two candidates are now in a rematch, with terrorism -- especially the subject of ETA -- a key campaign issue. The opposition conservatives have accused the Socialist government of being too soft on terrorists. E-mail to a friend
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