Madrid, Spain (CNN) -- French police arrested four suspected members of the outlawed Basque separatist group ETA late Thursday, including the armed group's alleged military chief and also the suspected logistics chief, the Spanish Interior Ministry said in a statement on Friday.
The arrests came during a unilateral cease-fire which ETA declared January 10, and is the second major blow against ETA in two weeks. On March 1, Spanish police arrested four key suspects in northern Spain.
French police rushed in late Thursday to the village of Willencourt, near the Belgian border, and detained Alejandro Zobaran Arriola, 29, the suspected military chief in charge of ETA commandos who carry out shootings and bombings, the ministry statement said.
Mikel Oroz Torrea, 31, the suspected logistics chief, was also arrested, along with two other men thought to be ETA militants.
Oroz was in charge of ETA's explosives, Spanish media reported, citing police sources.
Police in Spain and in France, ETA's traditional rearguard base just across the border, have in recent years arrested in succession various suspected ETA military chiefs, one after the other, as ETA replacements step in to fill the vacant position at the top.
ETA is blamed for more than 800 deaths in its decades-long fight for
Basque independence and is listed as a terrorist group by the United States and
the European Union.
Spain's Socialist government has vowed not to ease police pressure on ETA during its cease-fire, despite the group's promise it would be "permanent, general and verifiable."
ETA has broken previous cease-fires, notably in 2006 when an ETA car bomb at Madrid's airport during the then-"permanent" cease-fire killed two men and caused extensive damage.
The four suspects arrested on March 1 in Spain's northern Basque region had tried to operate under police radar screens, carrying on ostensibly law-abiding lives but secretly working for ETA, authorities said. Police seized 200 kilograms (440 pounds) of explosives in those raids.
Spanish media, citing police sources, said the suspects from March 1 are linked to ETA's killing two years ago of a police intelligence officer in the Basque region.
On January 18, a week after ETA's latest cease-fire announcement, police
arrested 10 people, most of them for alleged links to a shadowy group called
Ekin, which authorities say passes directives from ETA's leadership to a string
of equally shadowy support groups.
"The government's anti-terrorist policy has not changed at all because
ETA has not definitively abandoned its weapons. And as long as it doesn't, the
police will continue to arrest them, one after another," Spanish Interior Minister Alfredo Rubalcaba said on March 1.