A strong tremor measuring 5.9 on the Richter scale shook the eastern Mediterranean earlier today.
There were no immediate reports of damage or injuries.
The Athens Geodynamic Institute said the earthquake's epicentre was between the Greek eastern Aegean islands of Kos and Astypalea, at a depth of 75 kilometres.
The tremor was felt in southern Greece and as far as away Cyprus and Egypt, particularly among residents of high-rise buildings.
Cairo residents, particularly those living on the upper floors of tower blocks, said ceiling lights swung and furniture rattled.
Seismologists gave conflicting reports of the quake's magnitude. The Athens institute measured the quake at 5.9; the Patras Geodynamic Institute gave the quake a 6.1.
The official Middle East News Agency quoted the National Geophysics Institute as saying the earthquake measured 6.4 on the Richter scale.