The Greek prime minister said Friday he had informed EU leaders about two Greek soldiers remanded in Turkey.
Addressing a news conference after the EU leaders summit in Brussels, Alexis Tsipras said: "We did our best to resolve the issue with Turkey...but it was not possible."
"We informed EU leaders about the two Greek soldiers," he added.
"Greece will keep the communication channels open with Turkey, and continue to support Turkey's EU membership.... [but] we are concerned about Turkey's attitude."
Two Greek soldiers had been remanded into custody earlier this month after they "inadvertently" crossed the border in northwestern Turkey.
The defendants had filed an appeal to a court in northwestern Edirne province, but it was rejected.