A 6.4-magnitude earthquake has struck off the coast of northern Greece, with tremors felt in neighbouring Turkey and Bulgaria.

According to the United States Geological Survey (USGC), the earthquake occurred around 77km (48 miles) south-southwest of Alexandroupolis, between the islands of Lemnos and Samothrace, at a depth of 10km (six miles). The USGC downwardly revised its initial reading of 7.2.

Police and fire brigade officials said there were no reports of serious casualties, although some shops and houses on the two Aegean islands suffered minor damage.

Antonis Chatzidiamantis, mayor of Lemnos, told Mega TV: "It lasted very long and it was very intense. We haven't got the full picture of the damage caused yet."

He added that one woman, identified by a police official as a British tourist, was slightly injured at Lemnos airport when part of the ceiling collapsed.

In parts of western Turkey, panicked residents rushed into the streets on Saturday as tremors from the earthquake shook buildings. The quake also affected Turkey's most populous city Istanbul, as well as the Aegean coastal city of Izmir.

Around 30 people were reported injured in the tourist province of Antalya after jumping out of their apartment windows in the western town of Canakkale.

In the southern Bulgarian city of Haskovo, where tremors from the earthquake were also felt, the country's Civil Protection Agency confirmed that there were no reports of any casualties.

Greek seismologists said the quake was "severe" and warned that aftershocks of a magnitude of more than 5.0 were likely.

Greece frequently experiences earthquakes but most cause no serious damage. However, a 5.9-magnitude earthquake which struck in 1999 killed 143 people. The same year, two massive earthquakes killed about 20,000 people in Turkey's densely populated north-western region.

In October 2011, more than 600 people died after a 7.2-magnitude earthquake rocked Turkey's eastern province of Van.