A search was underway Sunday for four suspected migrants, three of them children, believed missing after trying to cross the river Evros from Turkey into Greece, local police said.
Twelve people overall were in a dinghy that sank on Saturday. Eight of them managed to swim to safety and alerted the authorities.
The river Evros has seen increased migrant traffic since Greek and EU naval patrols intensified in the Aegean in 2016.
Migration minister Dimitris Vitsas in October said numbers had increased dramatically, from more than 3,000 in 2016 to 5,500 in 2017 and some 12,000 up to that point last year.
Migration is among the issues to be discussed during a visit to Turkey next week by Greek Prime Minister Alexis Tsipras.