French police displayed video surveillance images on Friday of five suspects in the killing of a police officer by a group believed to belong to the armed Basque movement ETA.
Nerin is thought to be the first French policeman to have been killed by ETA, if it was responsible.
ETA wants independence for traditional Basque lands in northern Spain and also southwestern France but has come under pressure after a string of arrests of senior leaders in Spain and France.
The images of the five suspects were taken in a supermarket on Monday morning, the day before officer Jean Serge Nerin was killed in a shootout near Paris.
His patrol had intercepted a vehicle speeding away from the scene of a car theft and was then fired on by gunmen in two other cars.
As well as the video images, police also published photographs of Joseba Fernandez-Aspurz, 27, who was arrested after the shooting and Arkaitz Aguirregabiria-del-Barrio, 27, whom they described as a senior leader of the ETA military wing.
President Nicolas Sarkozy pledged on Thursday to punish Nerin's killers "with the utmost severity". Spanish Prime Minister Jose Luis Zapatero is expected to attend a memorial service for him next week.
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 French security measures 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 Gogea, was arrested in Normandy along with two suspected accomplices.
ReutersGüncelleme Tarihi: 20 Mart 2010, 12:26