Two earthquakes have struck south-western Greece, both with preliminary magnitudes of 5 but with different epicentres, seismologists said.
No injuries or damage were immediately reported.
The first quake struck at 5.12am (0312 GMT) on Sunday, with an epicentre beneath the seabed 69 kilometres (43 miles) south-west of the Ionian island of Zakinthos, the Athens Geodynamic Institute said.
The second struck more than two hours later off the south-western shore of the Peloponnese.
The US Geological Survey gave the first quake a preliminary magnitude of 4.9, and the second 5. Preliminary magnitudes often vary in the early hours after a quake.
Greece is in an earthquake-prone region, but most have epicentres deep beneath the seabed and rarely cause damage or injuries.