Early Saturday, a bus carrying migrants hoping to catch a boat to the Greek island of Lesbos overturned and rolled into a gorge in the western Balikesir province, killing seven Syrians and the driver, state-run Anatolia news agency said, AFP reports.
Forty-two others were injured, it said.
In a separate incident a day earlier, a bus carrying migrants from Syria, Afghanistan and Myanmar slammed into a car in the northwestern Canakkale province, killing six Syrians and injuring 30 others.
They were also being driven to a beach from where they would have tried to cross to Lesbos, it said.
Turkey, which is home to some 2.2 million refugees from Syria's civil war, has become a hub for migrants seeking to reach Europe, many of whom pay people smugglers thousands of dollars for the risky crossing.
This week, the bodies of 36 migrants, including several children, were found washed up along the Turkish coast after their boats sank while crossing the Aegean Sea to EU member Greece.
The European Union has pledged to give Ankara three billion euros ($3.2 billion) as well as political concessions in return for its cooperation in tackling Europe's worst migrant crisis since World War II.
But earlier this week, the EU said it was far from satisfied with Turkey's cooperation in stemming the flow of migrants trying to reach the bloc.