The suspected military leader of Basque separatist rebel group ETA has been arrested in south western France, the French interior ministry said today, the biggest blow to the organisation in months.

Garikoitz Aspiazu Rubina, known by his alias "Txeroki" or "Cherokee", was arrested in France's mountainous Pyrenean region, near the Spanish border, said the interior ministry statement, which misspelled his surname as Asiazu.

The ministry said Aspiazu was suspected of having killed two Spanish civil guard police in December 2007. Spanish media have also cited security forces blaming Aspiazu for ordering the car bombing of Madrid airport in December 2006 which killed two people and wrecked peace talks with the Spanish government.

"This arrest shows again the resolute commitment of the French police and gendarmerie in the fight against all forms of terrorism and illustrates once again the excellent cooperation between France and Spain in the fight against Basque terrorism," the statement said.

It was the latest in a series of captures of senior ETA figures and appeared to be the biggest blow to the organisation since ETA's then top commander Francisco Javier Lopez Pena was arrested in the French city of Bordeaux in May.

But, while arrests have come regularly and the Spanish government says the group has been reduced to a relatively small number of fighters, ETA has continued to carry out regular bombings.

ETA, which initiated its fight for independence of the Basque Country in northern Spain in the late years of the dictatorship of Francisco Franco in the 1960s, has killed more than 800 people in four decades.

With the Basque Country already enjoying considerable autonomy over areas including education and health and state support for the Basque language, the group has become increasingly isolated.

Polls indicate most Basques do not want independence and there have been media reports of disagreements between ETA and its outlawed political wing Batasuna.