Police arrested two suspected leaders of Basque separatist guerrilla group ETA in southwestern France yesterday, Spanish officials said. Spanish officials said the man and woman, who they identified as Ibon Fernandez Iradi and Ainhoa Garcia Montero, were arrested near Bayonne in a joint operation by French and Spanish police. Spanish Interior Minister Angel Acebes said Spanish authorities believed Fernandez Iradi was the head of ETA's operational units -- groups of ETA guerrillas who carry out bombings and shootings. Spanish sources said Garcia Montero was also believed to be part of the leadership of ETA's operational units. It is another very harsh blow to the organisational structure of ETA, Acebes said. Earlier, French police said they had arrested two suspected Basque separatist guerrillas during routine checks of motorists on a road in the southwest of France yesterday. They did not identify the suspects. The suspects, who were armed, were taken for questioning in Bayonne in the Basque region spanning the borders of France and Spain, French police said. Spanish officials said Fernandez Iradi and Garcia Montero were believed to have replaced Juan Antonio Olarra and Ainhoa Mugica, who were described by the Spanish government as top ETA leaders when they were arrested near Bordeaux in September. Listed as a terrorist organisation by the European Union and the United States, ETA has killed 838 people since 1968 to press its demands for an independent state in Basque areas of northern Spain and southwest France. The latest arrests come two days after two suspected ETA members were arrested in Spain following a shootout in which a Spanish policeman died. The Spanish government said on Wednesday that those alleged ETA members, who officials said were transporting 130 kg of explosives, planned a deadly New Year's Eve bombing spree in Madrid. French and Spanish police have stepped up cooperation in the fight against ETA, arresting dozens of suspects on both sides of the Pyrenees in recent months.