Suspected activists of the armed Basque separatist group ETA made a failed attempt at a major bomb attack overnight, Spanish police said Monday. The group parked a car containing about 80 kilos of explosives in front of a defense ministry delegation in the centre of the northern city of Logrono, the German news agency "DPA" reported. Only a small explosion occurred inside the car, causing slight material damage but no injuries. Officials said the blast was caused by the detonator of the bomb which had failed to function properly. Explosives experts rendered the bomb harmless and lifted the security cordon on Monday morning. Two vessels filled with explosives had been attached to the floor of the car. The vehicle also contained an oil drum, apparently aimed at sparking a fire to destroy evidence.