Three migrants were hospitalised Friday after a brawl in a camp on the Greek island of Chios, aid groups and media said, as the country prepared to begin returning migrants to Turkey under an EU deal.
The agency said police used stun grenades to restore calm during the late-night fight -- the second such incident within two days in Greece -- which caused serious damage to the island's Vial camp, including the medical dispensary, state ANA news agency said.
Medical charity Doctors of the World (MDM) said it had pulled out of the camp to protect its staff.
"The dispensary was almost entirely destroyed and security was no longer sufficient," MDM spokesman Evgenia Thanou told AFP.
Some 700 refugees and migrants on Friday were heading towards another camp in the main town of Chios under police escort, state TV ERT said.
Pro-migrant activists said the trouble began after a demonstration Thursday evening by migrants demanding they be allowed to leave the camp.
There has been anger among migrants and criticism from aid groups over EU plans to imminently begin sending thousands of people denied asylum back to Turkey.
Eight migrants were also hospitalised early Thursday after a fight between Syrians and Afghans in the overcrowded migrant camp at the Greek port of Piraeus near Athens.
Chios is home to one of five "hotspot" centres set up to house and process migrants on the Greek islands, which have been struggling to cope with an influx of migrants, many fleeing the civil war in Syria.
The Vial camp houses 1,500 people at a site which has capacity for just 1,200, ANA said.
Turkish Prime Minister Ahmet Davutoglu confirmed on Thursday that migrants would start being sent back from Greece to Turkey on Monday, under the terms of last month's controversial EU-Turkey deal.
Under the agreement, all irregular migrants landing on the Greek islands after March 20 face being sent back to Turkey -- although the deal calls for each case to be examined individually.
For every Syrian sent back from Greece, the EU has agreed to resettle one Syrian refugee directly from Turkey.
Over 51,000 refugees and migrants seeking to reach northern Europe are already stuck in Greece, after Balkan states sealed their borders. Hundreds more continue to land on the Greek islands on a daily basis, despite the EU deal.
Aid groups have criticised the EU-Turkey deal on ethical grounds, warning that the Greek registration sites would become de facto detention centres for people slated to be sent back to Turkey after risking their lives and spending a small fortune to try reach Europe.
They have also raised concerns over the conditions migrants face back in Turkey, which is already hosting an estimated 2.7 million Syrians, most of whom have been forced to fend for themselves given limited space in the country's refugee camps.