A rucksack bomb packed with around 10kg explosives caused what Local Police are describing as "minimal damage" to the municipal courthouse building in Tolosa (Guipúzcoa) when it detonated at around 1.15am this morning.

A warning call was made by an ETA representative to the DYA traffic office at 0.47am, allowing time for police to cordon off the area, and nobody was injured.

The blast affected a 3m diameter section of the courthouse façade and shattered all the windows as well as those of several other adjacent buildings and cars parked near the scene.

Since the Supreme Tribunal upheld the government's petition to ban the radical ANV and PCTV parties last month, there has been a marked escalation in ETA's terror campaign with three car bomb attacks between September 21st-23rd.

The last of these claimed the life of a 46-year-old army staff sergeant, Luis Conde de la Cruz, who had been staying at a military academy in Santoña. Six others were seriously injured in the attack.

These incidents followed a failed attempt on September 16th to assassinate a National Police officer based in Basauri, who drove 10km with a dud limpet mine attached to the underside of his car.