In the deadliest incident, the coastguard said it recovered the bodies of 14 people from a wooden boat which was heading from the western province of Canakkale to the Greek island of Lesbos when it crashed into rocks and took on water.
Another four perished when their vessel sank off the coast of Izmir, a province further south, the coastguard said.
“Must there be another Aylan for the world to wake up? Humanity is watching from the sidelines,” President Recep Tayyip Erdogan said on hearing of the latest tragedies.
He was referring to three-year-old Syrian refugee Aylan Kurdi, whose body was pictured washed up on a Turkish beach in September in images that shocked the world, pressuring European leaders to step up their response to the crisis.
Turkey, which is hosting 2.2 million refugees from the conflict in neighbouring Syria, has become the main transit point for people fleeing war and misery for a better life in Europe.
Dogan news agency said seven children were among those who died on the boat that sank off Canakkale while 27 people were rescued, among them a pregnant woman.
Survivors were taken to a nearby medical centre and were said to be in good condition.
Coastguard workers backed by helicopters were continuing a search for one person still believed to be missing.
“The boat probably sank after hitting rocks. It was severely damaged and apparently started to take in water but they decided to go ahead anyway,” Canakkale governor Hamza Erkal told Anatolia news agency.
“They apparently turned back after the boat took in more water but it sank before reaching the shore.”
There was no immediate information on the nationalities of those on board.
The coastguard said fisherman rescued another 22 from the boat off Izmir, while the hunt was going on for two missing.
‘Humanitarian support’ –
The latest tragedy came as European leaders were due to meet African counterparts in Malta to discuss the migration crisis.
There has been a sharp spike in the numbers of migrants and refugees setting out from Turkey for the European Union.
An EU report on Turkey released Tuesday was highly critical about the state of the rule of law and freedom of expression but praised its “humanitarian support” for the refugees and said the EU had to step up its cooperation with Ankara to tackle the crisis.
Last month, the EU announced a refugee cooperation deal with Turkey including a possible three billion euros ($3.3 billion) in aid.
The UN refugee agency UNHCR said last week up to 600,000 migrants and refugees were expected to cross from Turkey to Greece and onwards over the next four months despite the onset of winter.
More than 650,000 migrants and refugees, mostly from Syria, Afghanistan and Iraq, have reached the Greek islands so far in 2015 using the eastern Mediterranean route, the International Organization for Migration (IOM) said on Tuesday. Of those, 512 people died.