A car bomb planted by suspected members of the militant Basque separatist group ETA injured 46 people overnight in the northern Spanish city of Burgos, hospital sources said on Wednesday.
The car had been parked behind police barracks where families of police officers live.
Thirty-eight of the injured were taken to hospital, but none of them were reported to be in a serious condition. The victims included police officers, their wives and children. Most of them had bruises or cuts from shards of glass.
The bomb caused considerable damage to the 14-storey barracks, ripping a part of its facade open and causing a side wall to collapse. It also damaged surrounding buildings, some of the residents of which were evacuated.
Officials attributed the attack to ETA, which marks the 50th anniversary of its formation on Friday.
The group usually gives advance warning of its attacks, but no warning was received ahead of this attack. ETA "meant to kill", said Juan Vicente Herrera, prime minister of the region of Castile and Leon where Burgos is located.
A larger number of victims was avoided because around half of the people living in the barracks of the paramilitary Civil Guard were on holiday.
ETA has killed about 850 people since its separatist campaign took a violent turn in 1968. This year's attacks have claimed one fatality, police officer Eduardo Puelles, who died in a car bombing in June.
The group, which is listed as a terrorist organization by the European Union and the United States, seeks an independent Basque state created out of northern Spain and southern France.