An earthquake with a preliminary magnitude of 6.2 has shaken western Turkey and the Greek island of Lesbos.
It was not immediately clear if the quake had caused any major damage in Turkey or Greece. Earthquakes are common in both countries.
Turkey's Disaster and Emergency Management said the earthquake was in the Aegean Sea at a depth of more than four miles and hit at 3.28pm local time.
Tremors were also felt in densely-populated Istanbul and in the western Turkish provinces of Izmir.
The private Dogan news agency showed residents in western Turkey leaving buildings.
State-run radio in Greece said hundreds of residents left buildings and waited out in the street in Lesbos' capital, Mytilene.
Authorities in Lesbos said dozens of homes were damaged in parts of the island and some roads were closed, but there were no reports of serious injuries.
"We are advising residents in affected areas of Lesbos to remain outdoors until buildings can be inspected," senior seismologist Efthimios Lekkas said.
In Turkey, 61-year old Ayse Selvi felt the tremors in her summer home in Karaburun near the quake's epicentre.
"My God, all the picture frames fell on the ground and I have no idea how I ran out. I'm scared to go inside now."
Her sister Seval Isci, 57, was ironing at home in Izmir when the earthquake hit and left her home along with the other residents of the building when the first aftershock hit.
"We were really scared," she said.
Turkey's emergency management agency said there were no reports of casualties in the country.
Two devastating earthquakes hit northwestern Turkey in 1999, killing some 18,000 people.