The US Geological Survey said that a 7.0-magnitude earthquake occurred off the coast of western Turkey on Friday, and initial reports indicate that buildings were damaged, but there were no immediate injuries.
The earthquake, which was felt by residents from Istanbul to Athens, hit the Turkish city of Izmir, which has a population of about three million.
"So far, we have received information about six collapsed buildings" in the Izmir province, which includes the city, Turkish Interior Minister Suleyman Soylu said on Twitter.
"Some of our citizens are stuck under the rubble," said Environment Minister Murad Corum, adding that he knew of five collapsed buildings.
Pictures on social media showed water flowing in the streets of Izmir from a clear height in the sea.
The US Geological Survey said the quake was recorded 14 kilometers (8.6 mi) off the Greek town of Nyon Carlovacion on the island of Samos in the Aegean Sea.
The disaster management agency of the Turkish government stated that the earthquake, which occurred at a depth of 16.5 km, was less with a magnitude of 6.6.
Turkish President Recep Tayyip Erdogan wrote on Twitter that he was ready to help "by all means available to our country."
Turkey is located in one of the most active earthquake zones in the world.
In 1999, a 7.4 magnitude earthquake struck northwestern Turkey, killing more than 17,000 people, including 1,000 in Istanbul.
Another earthquake in 2011 in the southeastern province of Van killed more than 600 people.