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.