At least 16 women migrants and one boy died when their vessel sank off the Greek island of Lesbos early on Thursday, in the second maritime disaster involving refugees in the Aegean Sea in under a day, the country's coastguard said.
The sunken boat was carrying about 40 people, the coastguard said, citing people who had been rescued so far. There were 17 bodies recovered, a coast guard official said. Ten women were rescued and around a dozen people were presumed missing.
The boat sank east of Lesbos, which lies close to Turkey's coast.
Greek Migration Minister Notis Mittarachi tweeted a call for Turkey to take "immediate action to prevent all irregular departures due to harsh weather conditions.
"Already today many lives lost in the Aegean, people are drowning in unseaworthy vessels. EU must act," he wrote.
In the earlier incident, Greek authorities rescued 80 migrants - among them 18 minors - whose boat sank after hitting a rocky area in stormy waters near the island of Kythira in southern Greece on Wednesday.
According to those rescued, 15 were still missing and a search and rescue operation was being conducted along the wider coast of Lesbos for migrants who may have made it to shore. Three were found trapped in a remote area.
"Strong winds blowing in the area are making our work difficult," coast guard spokesman Nikos Kokkalas told state TV ERT.
Greece was at the front line of a European migration crisis in 2015 and 2016, when around a million refugees fleeing war and poverty in Syria, Iraq and Afghanistan arrived in the country, mainly via Turkey.
The number of arrivals has fallen sharply since then. But Greek authorities say they have recently seen a sharp increase in attempted entries through the country's islands and land border with Turkey.
On Thursday, Shipping Minister Plakiotakis accused Turkey of not preventing human traffickers from exploiting migrants and urged it to respect a 2016 deal with the European Union to keep refugees and migrants away from Europe.
"As long as the Turkish coast guard does not prevent their actions, traffickers will pile unfortunate people, without safety measures, into boats that cannot withstand the weather conditions," he said.
Turkey says it has ramped up measures in recent years to prevent people smuggling, while repeatedly accusing Greece of pushing back migrants and sinking their boats, something that Athens denies.