Spanish police arrested yesterday 13 people linked to groups that support ETA prisoners on suspicion of being active members of the Basque separatist guerrilla organisation, officials said. In the latest in a string of arrests of ETA suspects, police seized the 13 in the Basque region and in neighbouring Navarre, the Spanish government's top representative in the Basque region, Enrique Villar, told state radio. He said the arrests were ordered by Spanish High Court Judge Baltasar Garzon -best known for his attempts to bring former South American dictators to justice - who is leading an investigation into ETA. Several of the people arrested early yesterday were members of Gestoras pro-Amnistia, which campaigns for a pardon for convicted ETA members. Others belonged to a group representing families of ETA prisoners. A source at Gestoras pro-Amnistia told Reuters the 13 detained were being held on suspicion of forming part of ETA. Spanish and French police have arrested several suspected ETA members in recent months including at least two people believed to be senior members of the organisation who were held in France in September and October. The crackdown is believed to have weakened ETA and its attacks have slowed in recent months. However, the group has recovered from police crackdowns in the past.