while the walls of several rooms were blasted off with damage visible up to the 14th floor of the building.

Rubalcaba charged that ETA was "undoubtedly trying to kill" people with the blast as it had not issued any prior warning.

"It was not just aimed at those working in the Civil Guards but also but also their families, which makes this particularly despicable. Fourty-one children could have been killed," he said at the scene of the bombing.

At least 64 people were injured, most of them suffering cuts from flying glass, the director of the regional health service, Francisco Javier Guisasola, told reporters.

Police earlier said at least 22 women and six children were slightly injured in the blast.

European Commission President Jose Manuel Barroso condemned the attack as "indiscriminate and savage."

"Iwant to express our firm condemnation of the attack on the Civil Guard barracks in Burgos," he said.

The EU expressed its "complete solidarity with the citizens and the democratic institutions of Spain in the fight against terrorism," he added.

ETA has frequently targeted the Civil Guard in its 41-year campaign to carve a Basque homeland out of northern Spain and southwestern France.

The latest attack came just two days before the 50th anniversary of ETA's founding, on July 31, 1959, by nationalist students inspired by Marxist-Leninist teachings.

The group, considered a terrorist organisation by the European Union and the United States, carried out its first planned killing on August 2, 1968 with the shooting of a policeman. It is blamed for the deaths of 825 people.

Spanish public television last month said