Police arrested four suspected members of armed Basque separatist group ETA and seized 330 pounds of explosives in raids in Spain and France today, sources close to the operations said.
Spanish police arrested two suspects in a pre-dawn raid on their home in the northern town of Berriozar, near Pamplona, the Interior Ministry said.
Police also seized arms and the haul of explosives there, 30 kg of it already assembled as bombs.
"The central nucleus of the commando cell has been taken out of action with the arrest of two paid killers," Interior Minister Mr Angel Acebes told a news conference.
"An imminent terrorist attack has been avoided," he said.
French police also arrested two suspected ETA members at their home in the French Basque country, a source close to the enquiry said.
Mr Acebes identified the two men arrested in Spain as Mr Joseba Segurola and Mr Ibai Aguinaga.
He said police were investigating whether the pair were linked to a May 30th bombing that killed two police officers in the northern Navarre region and a bomb planted in a hotel in Pamplona Sunday during the town's fiestas.
ETA has been blamed for some 840 deaths in a 35-year campaign for an independent state carved out of northern Spain and southwestern France and it claims responsibility for 46 killings since it resumed violence in January 2000 following an 18-month cease-fire.