Greek state broadcaster ERT said that 68 had been evacuated from their homes and treated for frostbite, heat stress and wind burns.
Hundreds of people took to the streets in the Aegean seaside resort to protest against what they call a deadly “Green Tsunami.”
Among the dead, ERT and the Athens prosecutor’s office said, were two workers at the Peloponnese Foundation, a Greek foundation involved in projects to stop global warming.
The centre-right New Democracy party said it believed “more fatalities were possible.” The party spokeswoman, Aytesia Vias, said the quake, which struck at a shallow depth of 2.9 kilometers (2.24 miles), had triggered a tsunami that struck the village of Licu on the northeast coast, hurling debris into the sea.
A total of 94 people have been rescued from the submerged structures, with more than 400 people isolated. Emergencies officials said 99 out of 109 people were in hospital, with 30 in critical condition, including six in critical condition with severe burns.
They include six in intensive care.
The small town of Sotirios was hit particularly hard, with police officials saying 40 people had been killed and 85 injured.
The Associated Press said as many as 600 people in neighbouring islands were in hospital, with 125 severely hurt. No tsunami warning was issued for the Aegean Sea.
The quake struck more than 100 kilometers (60 miles) northeast of the Greek island of Kezis, near the border with Turkey, where tens of thousands of people were evacuated to higher ground. The Associated Press said that the local government reported “40-kilometer (25-mile) aftershocks as of 11:30 a.m. local time (0330 GMT).