An earthquake measuring 6.4 on the Richter scale has struck near the Greek coast and was felt as far away as
Italy and the Gaza Strip, but there were no immediate reports of injuries or damage.
The European-Mediterranean Seismological Centre reported a quake of magnitude 6.4 centred off the south-eastern tip of the Peloponnese Peninsula at a depth of 69 kilometres.
The quake struck at 1134 GMT (2234 AEST ) on Sunday and lasted for about seven seconds.
Greek television said it was felt as far as 300 km north of the capital and to the south on the island of Crete.
"The building started shaking, then there was a two second break and then it shook even stronger," a Reuters reporter in Athens said.
There were also reports it was felt as far away as Italy, the island of Cyprus and the Gaza Strip.
Italian media reported that the earthquake was felt across much of southern Italy, from the Adriatic port city of Bari to the Mediterranean port city of Naples.
The tremor came a day after a small earthquake measuring 4.5 on the Richter scale was registered off the coast of the Greek island of Cephalonia.
No damage or injuries were reported on Cephalonia or the island of Zante, where residents felt the ground shake early Saturday morning.
In September 1999, an earthquake measuring 5.9 on the Richter scale struck Athens, killing at least 143 people and leaving 60,000 people homeless.