French police were searching for at least six suspected members of the Basque separatist movement ETA today after a French policeman was shot and killed.
The unnamed 52-year-old officer was part of a patrol that was attacked after it halted a speeding car in Dammarie-les-Lys, a suburb east of Paris late yesterday.
The police came under fire from other vehicles, which were apparently committing several car thefts from a garage.
"We think it was a commando unit of at least six people, maybe 10, including a woman, because six cars were stolen," a French judicial source said.
One man was arrested at the scene and he gave a Spanish identity corresponding to that of a Basque individual close to ETA, according to the same source.
If ETA was responsible for the shooting, it would be the time the group has killed a French law enforcement official. ETA wants independence for traditional Basque lands not only in northern Spain but also in southwestern France.
Authorities in Spain, where the Basque separatist rebels have killed more than 850 people, were quick to blame the group.
"This time France has paid a high price for its collaboration in the fight against ETA, which is so important for our freedom and our security," Spanish prime minister Jose Luis Rodriguez Zapatero told a news conference.
"I feel just as strongly about the murder of this policeman as I would have done if he had been a member of our own security forces," he said.
ETA members have often used the open border with France to escape detection in Spain and while they do commit crimes, such as theft of vehicles and weapons, they avoid direct confrontation with French police.
However, in recent weeks increased security measures by the French have led to hundreds of arrests and seriously weakened the group.
At the end of February, the man believed to be ETA's military leader, Ibon Gogeaskoetxea, was arrested in Normandy along with two suspected accomplices.
Yesterday's killing was unlikely to herald a more aggressive attitude towards the French authorities, according to Juan Aviles, a history professor at Spain's UNED open university.
Instead, they may be struggling to operate effectively.
"You get the impression that they're improvising, that they lack professionalism as criminals."
Until yesterday, ETA had not claimed a fatal victim since July, when it killed two police officers on the island of Majorca with a bomb.
Polls indicate a significant minority of the inhabitants of the Spanish Basque Country, where Basque language and culture have remained distinct, would like independence, although only a smaller number sympathise with violent groups.
In the French Basque Country, the distinctive Basque language is no longer widely spoken and separatist sentiment is weak.