The president of France and the prime minister of Spain paid tribute in a solemn ceremony Tuesday to a French police officer allegedly killed by the Basque separatist movement, ETA, AP reported. French President Nicolas Sarkozy vowed to eradicate «one by one» ETA bases in France and said the killers of Jean-Sergei Nerin would be punished with «extreme severity» once caught. He appeared with Spanish Prime Minister Jose Luis Rodriguez Zapatero. Nerin, a 53-year-old father of four, received full honors during a ceremony in Melun, 30 miles (50 kilometers) southeast of Paris, close to where he was fatally shot a week ago by a suspected ETA commando unit. The Basques militants were allegedly trying to steal several vehicles from a used car dealershop. The killing marked the first time ETA has been accused _ by both France and Spain _ of the death of a French police officer. The organization uses France as a refuge and a logistics base for attacks it carries out in Spain. ETA has killed more than 825 people in Spain during a campaign launched in the 1960s to create a Basque homeland along the Atlantic coast in an area that encompasses part of northern Spain and southwestern France. Spain, France, the European Union and the United States consider ETA a terrorist organization. Spain on Monday raised its terrorism alert level due to the Nerin slaying from a «low intensity» alert to «high intensity» within stage 2 of the four-stage alert scale. «The killers of Jean-Serge Nerin will be found and will be punished with the most extreme severity,» Sarkozy said. «We won't let France become a support base for terrorists and assassins.» Using very strong language, Sarkozy said «no cause» justifies «blind violence, assassinations and barbarism.» Sarkozy posthumously decorated the officer with the French Legion of Honor. The French national anthem, the Marseillaise, was played and a minute of silence was observed. Both the French and the Spanish leaders extended their condolences to Nerin's family. France and Spain have stepped up their campaign against ETA members operating in France in the past two years. Ibon Gogeascoechea, the organization's alleged leader, was arrested in France on Feb. 28. He and two other suspected ETA members had been hiding out in a cottage rented with false identity papers. He was the fifth ETA leader arrested in Spain or France since May 2008. Sarkozy said 33 members of ETA had been arrested in France last year. The suspect in the Nerin killing is a Spanish Basque wanted on a European arrest warrant. -- SPA