A 6.1-magnitude earthquake struck south of the Greek island of Kasos on Wednesday, the United States Geological Survey said, but there were no immediate reports of damage. 

The offshore quake hit at a depth of 78.4 kilometres (49 miles), about 15 kilometres from the island's capital of Fry at 1:51 am (22:51 GMT Tuesday). 

Greece is located on a number of fault lines, and is sporadically hit by earthquakes.  

Between January 26 and February 13, more than 18,400 quakes, mainly of a low magnitude, were recorded off islands in the Cyclades archipelago, according to the University of Athens (EKPA) seismology laboratory. 

The seismic swarm caused no casualties or significant damage, but worried authorities and residents.