At least 20 people were missing and 40 rescued, the Turkish Coast Guard said. Their nationalities or where they were heading to was unknown.
A fishing boat carrying migrants sank off Turkey's coast in the Black Sea early on Friday, killing at least fifteen and leaving 20 others missing, the Turkish coast guard said.
At least 40 migrants have been rescued so far by coast guard boats and commercial ships, the Coast Guard Command said in a statement.
The fishing vessels sank just before dawn off the coast of Kefken, about 200 km (125 miles) east of Istanbul, the coast guard said. It said a coast guard plane and two boats were dispatched to the region after a commercial ship reported a distress signal from a fishing vessel.
There was no information on the nationalities of the migrants or where they were heading to. Migrants, however, are increasingly trying to cross the Black Sea from Turkey to reach Romania.
Ambulances and medical teams were sent to the port of Kefken and were waiting for boats carrying the rescued migrants.
The coast guard plane, a helicopter, three vessels as well as five commercial ships had joined the search and rescue effort, the coast guard said.