Its epicentre was located just off the island of Kythira about 200 kilometres (120 mi) south of Athens.
One person was injured and a number of buildings and roads in Kythira were heavily damaged as a result.
Several older houses on the island completely collapsed while the central square of the village of Mitata partially fell into the valley as a result of a subsequent landslide.
Nevertheless, despite the magnitude and the duration of the tremor (buildings in Athens swayed for almost 40 seconds) no other significant injury or damage was reported in the country's strongest earthquake in decades.
The tremor was felt as far away as in Bari on the Adriatic Sea, Naples and much of southern Italy, Malta, Cairo and even along the Lebanese, Syrian and Israeli shorelines.