A strong quake of magnitude 6.8 struck off Greece near the holiday islands of Zante and Kefalonia early this morning, with shaking felt 500 miles away.
The quake was at a depth of 10 miles, 22 miles west of Lithakia, a village in the southern part of Zante.
The tremors sparked a small tsunami of 15-20cm on local beaches, according to monitoring group EMSC.
A fire brigade official in Athens said there were no early reports of damage or casualties, but experts said a local tsunami could not be ruled out.
It struck at 1.54 am and was followed about half an hour later by a 5.2 aftershock.
One witness posted online: 'Me and my partner are staying in Zante, it woke my partner up, and we've had 3 aftershocks much smaller, the larger quake has moved several items around the room.'
Describing the tremors, one person living in Greece told EMSC they felt: 'Extremely violent shaking. Objects fell off of shelves. Loud rumbling sound.'
Others also described it as 'strong' or 'very strong,' saying the shaking lasted 15 to 30 seconds.
Greece lies in one of the world's most earthquake-prone regions, with thousands of quakes recorded every year. But few cause injuries or significant damage.
Zante has had severe earthquakes in the past, and as a result has a very strict building safety code.