A bomb exploded outside a court house in Spain's northern Basque region on Saturday, causing considerable damage but no injuries, AP quoted sources of regional police as saying. The detonation in the town of Tolosa was preceded by a telephone warning to a regional road rescue service by a man who said he spoke on behalf of Basque separatist group ETA. The caller said a bomb would explode by the court house at 1:15 a.m. Saturday. Officers rushed to the scene where they found a rucksack and proceeded to cordon off the area, a police statement said. The rucksack exploded at the announced time and blew a large hole in the courthouse, breaking glass all around the building and damaging cars. As an organization, ETA normally doesn't claim responsibility for its attacks until weeks after they occur.