Four women and five children died on Friday after their migrant boat sank off the Turkish coast, the coastguard said.
The boat went down off Balikesir province in western Turkey, the coastguard said in a statement, without giving the nationality of those on board.
Five other passengers were saved from the boat, which was heading for the Greek island of Lesbos.
The boat had been carrying 17 people and it was not immediately clear what had happened to the rest.
Turkey has around four million migrants and refugees, mostly Syrians, and is also a key transit country for those fleeing the Middle East towards Europe.
Under an agreement reached with the European Union in 2016, Turkey has made greater efforts to limit departures towards the five Greek islands closest to its shores.
That has led to a dramatic drop in the number of arrivals on Greek islands — from 875,000 in 2015 to under 40,000 per year in 2017 and 2018, according to Frontex, the EU’s border force.