A strong 5-magnitude tremor hit just west of the Greek island of Cephalonia in the Ionian Sea in the early hours of Sunday.
The quake, which hit at 1.15 a.m. local time, had its epicenter 5 kilometers underwater, the Athens Geodynamic Institute reportsed
There have been no immediate reports of damage or injuries.
A 4.7-magnitude quake had hit the island on Friday.
The area often produces very strong quakes. The island was flattened in 1953 by a 7.2-magnitude tremor.