Thousands of people in the Spanish city of Bilbao demonstrated against the Basque separatist organization ETA on Saturday, one day after the murder of a policeman in the region, according to dpa. Under banners reading "For Freedom, No to ETA," the demonstrators marched through the streets of the Basque city on Saturday evening. On Friday, police officer Eduardo Puelles Garcia, 49, died when a bomb attached to his car exploded in the town of Arrigorriaga. The government blamed the attack on the militant Basque separatist group ETA. The killing was the first attributed to ETA since socialist Patxi Lopez became Basque regional prime minister in May. The victim's wife and two sons attended the march. The regional premier had on Friday called Puelles a "defender of the Basques." Demonstrations against ETA had already taken place in other Spanish towns and cities during the afternoon. ETA had vowed to target the government of Lopez, who is the first Basque premier clearly defending the region's unity with Spain, and has announced plans to step up the fight against ETA. Since the Basque region was granted a wide autonomy in 1979, it had been governed by the Basque Nationalist Party (PNV), which has separatist currents. The Basque parliament Friday observed a moment of silence in a tribute to Puelles. ETA, which is regarded as a terrorist group by the European Union and United States, has killed more than 820 people in its four- decade campaign for an independent Basque country created out of northern Spain and southern France. Puelles was ETA's first mortal victim in 2009. The group is blamed for four deaths in 2008. ETA has grown increasingly weak, with its support dwindling and hundreds of its members detained in the recent years. Zapatero's government tried to negotiate with ETA in 2006. The attempt collapsed when ETA violated its ceasefire with a car bomb in the end of the year.