At least 27 refugees and migrants have died off the Turkish coast trying to reach the Greek island of Lesbos, Turkish media say.
The victims, including 11 children, drowned when their boat capsized after setting off from Balikesir province.
About 400 people have died crossing into Europe in 2016, the International Organization for Migration (IOM) says.
Most were travelling to Greece on their way to northern Europe. Recent fighting in Syria has sent thousands of people fleeing towards the Turkish border.
The sea route from Turkey to Greece was the most popular way for migrants trying to enter Europe in 2015.
In the latest incident, Turkish media quoted official as saying that 40 migrants set out for Lesbos from the Altinoluk area early on Monday. They said the boat capsized 3.2km into the crossing.
Hurriyet newspaper said the vessel was using a new route, because security forces have stepped up moves to deter migrants from taking their chances.
The paper also denied earlier media reports that another migrant boat had capsized further south off Izmir province.
News of the deaths came as Germany's Chancellor Angela Merkel was in Turkey to discuss ways of reducing the number of migrants travelling to Europe.
After talks with Turkish Prime Minister Ahmet Davutoglu, Mrs Merkel said they had agreed to seek help from Nato - both countries are members - in handling the migrant crisis.
She said they would use the next meeting of the alliance to consider "to what extent Nato can be helpful with the surveillance situation at sea'' and support the EU border agency Frontex.
The IOM says more than 68,000 migrants arrived on Greek shores in the first five weeks of 2016, despite often stormy conditions. This is a huge rise from last year, when the figure for the whole of January was less than 1,500.
Nearly half of those who have arrived in Greece this year are from Syria, the IOM says.
But thousands of Syrians seeking to flee a government offensive in Aleppo, backed by Russian air strikes, are being prevented from leaving their homeland.
Turkey has so far closed the border to most of the 30,000 migrants gathering at the Kilis border crossing, despite appeals by EU leaders to let them cross.
After her talks in Ankara, Mrs Merkel said: "In the past days we have been not only shocked but horrified by the human suffering of tens of thousands of people through bomb attacks predominantly carried out by the Russian side."
Mr Davutoglu said his country would accept the migrants "when necessary", and that it would reveal plans next week to slow the flow of arrivals.