Five Afghans, including a baby and two small children, have drowned as they tried to sail from Turkey to Greece.
The vessel, which was transporting Afghan and Iranian refugees and migrants to the Greek island of Lesbos, foundered just 500 metres from the Turkish coast.
Turkish coastguards managed to save nine of those on board while two are still missing.
One of the victims from last night's capsize, in which their boat hit rough weather as it travelled towards the Greek island of Lesbos, managed to swim ashore but died during attempts to revive him, a coastguard official said.
Of the four bodies found at sea, one was that of a six-month-old baby, rescuers said.
The deaths come as the European Union and Turkey are trying to firm up a proposed deal to end the migration crisis.
On Monday, Turkey proposed a deal that would see the EU resettle one Syrian refugee from camps in Turkey in exchange for every Syrian that Turkey takes from Greece, in a bid to reduce the incentive for people to board boats for Europe.
In return, Turkey wants billions of euros in aid, visa-free access to Europe's passport-free Schengen zone and a speeding up of Ankara's efforts to join the EU - demands that go too far for some.
EU leaders hope to finalise the deal at a summit next week.
Turkey's EU Minister Volkan Bozkir said the deal does not apply to those who have already reached the Greek islands and that the number returned was ultimately expected to be in the thousands or tens of thousands.
"Forming the mindset that 'You can't go there anymore, there's no hope there' is the basis of preventing [illegal migration]," Mr Bozkir told the state-run Anadolu agency.
He also said Turkey would meet by 1 May the EU's conditions for visa-free travel to Europe, seen by many Turks as the main benefit of the deal.
EU leaders set requirements including changing Turkey's visa policy towards Islamic states and introducing harder-to-fake biometric passports
Turkey has become the main launch pad for refugees fleeing the five-year civil war in Syria in search of a better life in Europe.
Some 850,000 people landed in Greece from Turkey last year, often in desperately unseaworthy vessels.
Since 1 January, more than 130,000 people have made the trip.
More than 35,000 people are trapped at the Greek-Macedonian border at Idomeni as Europe tries to close the Balkan route to people fleeing violence and economic upheaval.
Mr Bozkir said the deal does not apply to those who have already reached the Greek islands and that the number returned was ultimately expected to be in the thousands or tens of thousands.
