Seven people have drowned after a boat carrying dozens of migrants capsized off the Greek coast.
Two children, four women and one man died after the boat overturned near the island of Lesbos.
Some 57 people were saved following a search and rescue operation, the Greek coastguard said.
Greece has become one of the main gateways for refugees coming into Europe in recent years, with many of them fleeing conflict in countries like Syria and Afghanistan.
Many people attempt to cross the Aegean Sea from Turkey, a short but perilous trip often hit by bad weather.
Although the number of people heading to the Greek islands from the Turkish coast has decreased since the height of the refugee crisis in 2015, hundreds continue to arrive each week.
Philippe Leclerc, the United Nations High Commissioner for Refugees representative for Greece, said: "This tragedy is a painful reminder that people continue to take perilous journeys to reach the Greek Aegean islands.
"Redoubled efforts are needed to ensure safe and legal ways to reach Europe, so people stop risking their lives in the hands of ruthless traffickers and smugglers."
Nearly 10,700 refugees and migrants have reached Greece so far this year by sea, and 39 people have lost their lives while attempting the journey.
Additional reporting by agencies.
