The Greek health authority registered 35,580 new coronavirus infections between Wednesday and Thursday, almost six times as many new cases as the same time last week, when the daily figure stood at 6,667.
The Omicron variant, which is now spreading largely in the greater Athens area, is thought to be driving the huge increase in cases.
In response, the government has tightened its anti-coronavirus measures.
From Thursday until at least January 17, restaurants must close at midnight and limit seating, though an exception allowing establishments to open until 2 am has been made for New Year's Eve.
In addition, higher grade FFP2 masks must be worn in supermarkets, on public transport and in other public spaces.
