A powerful earthquake of magnitude 6.7 killed at least two people when it struck near major Turkish and Greek tourist destinations in the Aegean Sea, Turkish and Greek officials say.
The quake, which struck at 1:31am (local time) on Friday, was located off the southwestern coastal city of Marmaris in the Mugla province, the USGS said.
It was close to the Turkish towns of Bodrum and Datca, and the Greek island of Kos in the Dodecanese Islands archipelago, all of which are major tourist destinations.
George Kyritsis, the mayor of Kos, told Reuters that at least two people were killed on the Greek island and several were injured by the quake.
"We have two dead and some people injured so far," Kos Mayor George Kyritsis told Reuters.
Greece's fire service said it had rescued three injured persons from a damaged building.
The chairman of Turkey's Disaster and Emergency Management Presidency (AFAD), Mehmet Halis Bilden, warned citizens about incoming aftershocks, and added there were no casualties or major damage in Turkey.
"Our people should know that aftershocks are continuing, so they should refrain from entering damaged or vulnerable structures," Bilden told broadcaster CNN Turk.
Data on AFAD's website showed at least 13 aftershocks (12 in Turkey and one in Greece) with five of them over 4.0 magnitude. One of the aftershocks was a magnitude 4.6 that struck at 1.52am.
Television footage from the Mugla province shows hundreds of people abandoning their buildings and waiting on the streets, as others ran away from buildings on roads. It showed cars shaking and products falling off shelves at stores across the region.
Mugla Governor Esengul Civelek told a news conference that initial reports showed there were no major damages and disruptions. She said a small number of people had suffered minor injuries and that authorities would provide supplies and assistance to citizens on the streets.
Mugla Mayor Osman Gurun said power outages affected certain parts of the province and that telephone operators experienced shortages due to overloads.
Bodrum Mayor Mehmet Kocadon said the earthquake had caused minor cracks on some old buildings.
The European quake agency EMSC said a small tsunami could be caused by the quake, but Turkish broadcasters cited officials saying large waves were more likely.
The temblor, initially reported as a magnitude 6.9, was very shallow, only 10 kilometres below the seabed, the USGS said.
Turkey's AFAD said the temblor had a magnitude of 6.3, while local authorities said the quake was felt across the Aegean coast.
A magnitude 6.7 quake is considered strong and is capable of causing considerable damage, but the effects of this one would have been dampened by striking in the sea.
Turkey is prone to earthquakes because it is located between the Arabian plate and Eurasian plate.
More than 600 people died in October 2011 in Turkey's eastern province of Van after a quake of 7.2 magnitude and powerful aftershocks. In 1999, two massive earthquakes killed about 20,000 people in the densely populated northwest of the country. A 5.9 magnitude quake in 1999 killed 143 people in Greece.
The EMSC reported a 25cm sea level rise in the region.
British tourists in the region reported feeling the quake.