Christmas concerts and other events have been canceled in Greece under new restrictions announced Thursday that include a general mask mandate for outdoors and all public areas.

Incoming travelers will also be required to have follow-up tests for COVID-19 on the second and fourth days after their arrival.

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The restrictions will take effect Friday as the country braces for the expected impact of the omicron variant of the coronavirus, with the public health service already under pressure and intensive care space at more than 90% capacity.

“Due to the large amount of Christmas activity and crowded conditions that it creates, the mandatory use of masks is fully justified,” Health Minister Thanos Plevris said during a live-streamed presentation of the measures, which will remain in effect at least through Jan. 3.

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Greece suffered a spike in pandemic-related deaths in November and December with the infection level easing in recent days. But the emergence of the omicron variant has renewed concern in the country where about a quarter of the adult population remains unvaccinated.

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Based on vaccine appointment data, Plevris said the adult vaccination coverage would soon rise to 80%. Nearly 30% of Greece’s population has already received a booster shot.