Madrid/Paris - Last night, French and Spanish police officers managed to detain the suspected military leader of the militant Basque separatist group ETA.

Mikel Garikoitz Aspiazu Rubina, known by his alias Txeroki, was held at 3:30 am with a woman near the Cauterets ski resort 30 kilometres from Lourdes in the Pyrenees in a coordinated operation between French and Spanish security forces.

The suspects were asleep when police broke into their flat, Spanish media reported. Both were armed.

Txeroki, 35, has been the reputed head of ETA military operations for the past five years, and was responsible for ordering and planning bomb attacks.

The woman was thought to be Leire Lopez Zurutuza, one of the most wanted ETA members, who is suspected of participating in several attacks.

Police searched the flat in the presence of the suspects, seizing fake documents and a computer.

French President Nicolas Sarkozy hailed the arrest as demonstrating "the excellent collaboration between France and Spain in the fight against Basque terrorism."

Spanish political parties welcomed the arrest as a big blow to ETA.

Txeroki was expected to be transferred to the French city of Bayonne later Monday, and to be extradited to Spain later on.

Known as particularly violent, Txeroki is held partly responsible for the collapse of an attempt at peace talks between the Spanish government and ETA in 2006.

His inflexible strategy is believed to have contributed to internal divisions between hardliners and moderates within ETA.

Born in the Basque city of Bilbao, Txeroki first joined radical separatist youths who commit acts of street violence.

He is believed to have entered ETA in 2000, participating in several attacks including the killing of a judge in 2001.

From 2004 onwards, Txeroki coordinated ETA cells, ordering the car bombing that killed two Ecuadorian immigrants at a Madrid airport underground parking lot in December 2006.

That attack prompted Prime Minister Jose Luis Rodriguez Zapatero's government to end a six-month attempt at peace talks with ETA.

Txeroki is also suspected of personally shooting dead two Spanish police officers in Capbreton, southern France, in December 2007.

The killings broke ETA's rule of not carrying out attacks in France, where the group has a large part of its infrastructure to keep clear of Spanish police.

Txeroki's arrest followed that of Francisco Javier Lopez Pena, regarded as ETA's top overall leader, in France six months earlier.

In its most recent attack, ETA injured about 30 people in a car bombing at a university campus in Pamplona, northern Spain, on October 30.

ETA, which has killed more than 800 people in its campaign for a sovereign Basque state carved out of northern Spain and southern France, has been listed as a terrorist organization by the European Union and the United States.