Several policemen, who were evacuating the area
suffered ear injuries and one was hurt in a fall [AFP]
A bomb has exploded outside an office of the ruling Socialist Party in the Basque city of Bilbao.
The explosion wounded seven police officers who cordoned off the area after a warning from Eta, police said.
The bomb, hidden in a bag, exploded at 6am (0400 GMT) on Thursday, half an hour after the telephone call told police where it had been placed, a police spokeswoman said.
The warning call was made in the name of Eta, the Basque separatist group, she added.
Several policemen, who were evacutating the area suffered ear injuries and one was hurt in a fall, she said.
Others were lightly injured by broken glass from the blast which caused considerable damage to the Socialist party office, another spokesman said.
Javier Balza, Basque interior department chief, told Spanish Cadena SER radio: "We had to evacuate old people, children, people who were in their houses sleeping at the time.
"The houses are badly damaged. In the end it's the people who suffer the madness of the terrorists."
The attack was immediately condemned by the Socialist party.
"Eta must know that it will make no political gains with violence, because in a democratic country like Spain, nothing can be gained by violently disrupting democratic and lawful norms," the party said in a statement.
The explosion came a day after Spain's King Juan Carlos called for political unity in fighting terrorism in Spain, at the inauguration of parliament following elections on March 9.
Jose Luis Rodriguez Zapatero, Spain's socialist prime minister beginning his second term in office, has leaned towards peace talks with the group, while the opposition People's Party have demanded tougher police action.
Eta has campaigned for an independent Basque country in northern Spain and southwestern France since 1959.
The group declared a ceasefire in March 2006, but ended it after it failed to win concessions in negotiations with Zapatero's government.
More than 820 people have been killed in four decades of Eta's armed struggle.