A magnitude 6.3 earthquake off the western coast of Turkey and between the Greek islands of Lesbos and Chios has shaken buildings from the Aegean Turkish province of Izmir to Greece's capital, Athens.
The epicentre of the quake was about 84km northwest of the Turkish coastal city of Izmir, the European-Mediterranean Seismological Centre said on its website.
There were no immediate reports of injuries in either Turkey or Greece, according to preliminary information from local authorities, although the quake was felt as far away as Athens.
Greek television stations reported some structural damage in the town of Plomari on Lesbos.
"The trembling was really bad. Everything in my clinic started shaking wildly, we all ran outside with the patients,"a dentist in Izmir's Karsiyaka district said.
"We are very used to earthquakes as people of Izmir but this one was different. I thought to myself that this time we were going to die."
Social media users who said they were in western Turkey reported a strong and sustained tremor.
"We will be seeing the aftershocks of this in the coming hours, days and weeks," the head of Turkey's Kandilli Observatory said, noting that the aftershocks could have magnitudes of up to 5.5.
Major geological fault lines cross Turkey and small earthquakes are almost a daily occurence.
More than 600 people died in October 2011 in the easternprovince of Van after a quake of 7.2 magnitude and powerful aftershocks.
In 1999, two massive earthquakes killed about2 0,000 people in the densely populated northwest.