Greek authorities were transferring around 570 migrants from an overcrowded camp on the island of Lesvos on Sunday, officials said.
A regularly scheduled ferry left Lesvos Sunday evening carrying the migrants, who used to live in the migrant camp of Moria.
Authorities say this is part of the plan to reduce overcrowding at the camp, where about 13,000 people live in a space designed for 3,000.
Migrants, most of them Afghans, have protested, sometimes violently, over the prevailing conditions, demanding their transfer out of Moria and a quick response to their asylum demands.
Authorities say the 570 are among what they term "vulnerable categories" — families, single women with children and unaccompanied minors.
The ferry will arrive at Piraeus, the main port in Athens, on Monday morning. The migrants will be moved to a camp near the northern city of Thessaloniki.