Officials said most of the injuries were due to people rushing out of buildings in panic during the shaking.
The 6.9 magnitude temblor was centered about 185 miles north-northeast of Athens near the Greek island of Lemnos and the Turkish island of Gokceada.
Seismologists said the quake struck at 11:25 a.m. local time at a depth of about 6 miles beneath the bed of the Thracian Sea. It was felt as far away as Bulgaria and Istanbul.
While two mosques and some other buildings near the epicenter sustained cracking during the quake, there were no reports of any structures collapsing.
Turkey's emergency and disaster management agency said there were about 70 aftershocks, the strongest registering a magnitude of 5.5.