An earthquake rattled Athens on Wednesday, causing buildings to shake for several seconds, Reuters witnesses said.
There were no immediate reports of casualties or damage, police and fire brigade officials said, and the streets of the capital were calm.
The magnitude 5.1 quake struck northeast of Patras at a depth of 9.7 miles, U.S. Geological Survey data showed.
"While the earthquake wasn't that strong it was felt because it was near the surface," an official at the Athens Geodynamic Institute said.
Greece is often rattled by earthquakes. While most cause no serious damage, a 5.9 magnitude quake killed 143 people in 1999.