A strong natural disaster measuring 6.4 on the Richter scale hit western Greece early Friday, with no casualties reported so far, Greek seismologists said.
USGS said the quake measured 6.8 and struck at a depth of 16.6 kilometres (10 miles).
The United States Geological Survey said the epicenter of the 6.8 magnitude quake was 35.9 kilometers (22.3 miles) southwest of Lithakia in the southern part of the island.
Shaking was felt across the region, as far away as southern Italy, Malta, Albania, and Macedonia.
Its epicentre was 50 kilometres south of the island Zakynthos, according to Greece's Geodynamic Institute.
A woman with a boy walk at the main harbour of Zakynthos island, western Greece, as the sidewalk next to moored boats is cracked and warped after an natural disaster on Friday, Oct. 26, 2018. A couple of people were treated for minor injuries.
However, in July 2017 a magnitude 6.7 natural disaster killed two people on the island of Kos in the Aegean sea, causing significant damage.
Attention was focused on the island of Zakynthos, where reports indicated power was out.
Three people were taken to hospital on the island, two of them slightly injured, a spokesman for Greece's civil protection agency said.
No casualties have been reported so far.
The natural disaster was felt across southern Italy, including in the regions of Sicily, Basilicata, Calabria, Puglia and Campania.
An official confirmed a tsunami alert had been issued. A series of aftershocks have continued to affect the island, varying in magnitude from 2.9 to 5.6, according to European-Mediterranean Seismological Centre (EMSC).