A magnitude 6.4 earthquake struck off the coast of northern Greece on Saturday, some 77 km (48 miles) south-southwest of Alexandroupolis, the U.S. Geological Survey said, according to Reuters.

The USGS said the quake's depth was 10 km (six miles). There were no immediate reports of casualties or serious damage.

Residents in Istanbul in neighboring Turkey felt a small tremor that lasted around 10 seconds.

Meanwhile, a source in Istanbul told a PanARMENIAN.Net reporter, that people rushed into the streets fearing of possible aftershocks. Mobile communication was down for about an hour. Tourists have been evacuated from some Turkish resorts, the source said.