Twenty-two migrants including seven children have drowned after a boat capsized off the Turkish coast, local officials said on Friday.

Two people were rescued by the Turkish coastguard and another two managed to make it out of the water on their own, officials said. The victims' nationalities were not yet known.

The boat capsized off Turkey's largest island, called Gokceada or Imbros, which is located in the Aegean Sea off the coast of the northwestern province of Canakkale, near Greece's Lemnos island.

"The Turkish coastguard found the bodies of 22 people including seven children," the local governor's office said in a statement.

The search and rescue operation was backed by one airplane, two helicopters, a drone, 18 boats and 502 personnel, it added.

Turkey is hosting nearly four million refugees, mostly Syrians.

Many migrants try to reach the Greek islands from Turkey's western coasts hoping to eventually reach prosperous European Union countries, with many dying in the perilous sea crossing.

Officials said the boat began sinking overnight and on Friday many ambulances were standing by at the port of Kabatepe near Gokceada.

There has been an increase in migrant crossing attempts in the waters between Turkey and Greece in recent weeks.

The Turkish coastguard indicated that it had rescued or intercepted several hundred migrants, including children, attempting to cross to Greece since the start of the week.

- More arrivals -

The EU border agency Frontex said this week that the number of irregular border crossings into the bloc in the first two months of this year reached 31,200 -- similar to the level from a year ago, according to preliminary calculations.

In the eastern Mediterranean, the second most active migratory route after the Western African route, the number of detections more than doubled to 9,150 in the first two months of the year, it said.

The Mediterranean Sea has for several years been the centre of migrant flows from Africa and the Middle East to Europe.

The influx peaked in 2015 as migrants, many fleeing the Mideast upheaval caused by Syrian civil war, sought refuge in Europe.

Turkey struck a deal with the European Union in 2016 to curb the number of arrivals to the EU in return for financial assistance and other incentives.

The issue of illegal migrants is a thorn in relations between NATO members Turkey and Greece, which are already embroiled in long-standing disputes from exploratory drilling rights in the eastern Mediterranean to the divided island of Cyprus and rival claims over the Aegean Sea.

Greece also frequently accuses Turkey of waving through migrants from across their joint border and at sea.

Ankara in turn accuses Athens of illegal pushbacks of migrant boats.

Turkey and Greece agreed when Turkish President Recep Tayyip Erdogan visited Athens in December to open a new page in their relations and address their problems including irregular migration through dialogue and mutual goodwill.

The issue of migrants is likely to figure highly in talks when Greek Prime Minister Kyriakos Mitsotakis visits Ankara in May.