Greek police say clashes have broken out between rival ethnic groups of refugees and other migrants at a detention camp on the eastern Aegean Sea island of Samos.
Police say six people have been injured and 25 detained. About 1,100 people are held in the facility.
Thursday's violence came a day after similar clashes at a camp on the island of Lesvos, which left three migrants hospitalized with injuries.
More than 8,000 people are held in detention on Greece's eastern islands following a March agreement between the European Union and Turkey to deport migrants and refugees.
Deportations have been held up by delays in the asylum screening process - triggering frequent unrest.
About 52,000 refugees and economic migrants have been trapped in Greece after a series of Balkan border closures. [AP]