The French government has blamed the Basque terror organisation ETA for the killing of a French police officer on Tuesday.
If correct, it is the first time a French police officer has been targeted by ETA.
French authorities are now looking for a group of about six suspects who fled after the shooting, which took place at a car sales yard near Paris.
As the suspects were leaving in six vehicles they had stolen, they opened fire on police who were patrolling nearby.
Police managed to apprehend one of the gunmen but not before a police officer was fatally wounded.
Both French and Spanish authorities are involved in the hunt for the suspects.
In the past few weeks hundreds of suspected ETA members have been arrested in France, including Ibon Gogeaskoetxea, a senior leader in the organisation.
