Greece said on Tuesday it would make COVID-19 vaccinations mandatory for people aged 60 and over in a move to quell a resurgent virus that is burdening a frail healthcare system.

Authorities said those who failed to comply from Jan. 16 would face a recurring monthly fine of 100 euros.

Tuesday's announcement marks an EU-wide first in targeting a specific age group. Other countries make vaccines mandatory for health workers and other high-risk groups of workers.

Prime Minister Kyriakos Mitsotakis said he struggled with the decision but it was necessary to protect more than half a million elderly Greeks who had failed to get the jab.

"Its the price to pay for health," he said.

About 63% of Greece's 11 million population is fully vaccinated. While vaccine appointments have picked up in recent weeks, health ministry data shows there are 520,000 people over the age of 60 who have failed to get a jab.

"We are focusing our efforts on protection of our fellow citizens and for this reason their vaccination will be mandatory from now on," Mitsotakis told a cabinet meeting.

Syriza, Greece's main opposition party, faulted the measures as being punitive and financially excessive.

"This hasn't happened anywhere," it said.

Mitsotakis did not say how authorities would enforce the rule. A 100 euro fine is a hefty chunk of the average monthly 730 euro pension.

"(The decision) tortured me, but I feel a heavy responsibility in standing next to those most vulnerable, even if it might fleetingly displease them," he said.

Greece this month barred unvaccinated people from indoor spaces including restaurants, cinemas, museums and gyms as daily COVID-19 cases hit record highs.

It has recorded 931,183 infections and 18,067 deaths since the start of the pandemic last year.