A boat carrying 45 migrants is sinking in the southeastern Aegean Sea, Turkey’s defense ministry said.
The vessel ran into trouble around 100 kilometres south of the Greek island of Karpathos on Friday, they added.
Several migrants were still missing on Friday morning off Crete after their boat sank, according to the Greek coastguard.
Thirty-seven migrants, mostly from Syria and Iraq, were rescued on Thursday evening, Greece said. According to survivors, there were a total of about 45 people on board the vessel.
The Turkish ministry said in a statement that two naval ships and one maritime patrol aircraft had been deployed in the rescue attempt.
Commercial ships were also issued "search sector" messages through a marine announcement system, but authorities have warned that sea and weather conditions for the search operation are "adverse".
Migrants have tried to cross the Aegean Sea from Turkey to Greece in the hopes of starting new lives in Europe.
A 2016 migration deal between Turkey and the EU has helped stem refugee flows but many still attempt the dangerous sea routes to try and reach one of the Greek islands.