The new countrywide restrictions will take effect from Saturday
Greece ordered a nationwide lockdown for three weeks on Thursday, its second this year, to help contain a resurgence of Covid-19 after a sharp increase in infections this week.
Prime Minister Kyriakos Mitsotakis said he was forced to act after a spike in cases in the past five days, saying that without a lockdown pressure on the healthcare system would be "unbearable."
"I've chosen to take drastic measures sooner rather than later," said Mitsotakis, who had previously said a nationwide lockdown was a last option.
Officials said that in the past week alone, there was a 20% increase in confirmed infections. From next Monday, people arriving by air will require proof of a negative coronavirus test, taken within 48 hours of travel.
Under the new countrywide restrictions, to take effect from Saturday, retail businesses will be shut with the exception of supermarkets and pharmacies. Greeks will need a permit to venture outdoors at allocated times.
Primary schools will stay open, but high schools will shut.
Greece registered 2,917 new infections on Thursday, its highest daily tally since the outbreak started in February. It had reported 2,646 infections on Wednesday, with infections hitting four-digits daily only in the past eight days.
So far, 702 people have died of Covid-19, 29 of them - a new high - on Thursday.
Thursday's announcement prompted a scramble by many to book pre-lockdown hairdresser and barber appointments. "Its been absolutely crazy, we haven't stopped to catch our breath," one barber in central Athens told Reuters.
Authorities later announced they would make an exception for hairdressers, allowing them to work two extra days until Monday to meet demand.
The main opposition, the leftist Syriza party, has criticized the government for failing to bolster the health system.
"The government has undermined the magnitude of this crisis," said Alexis Haritsis, Syriza MP and former interior and deputy finance minister.
Greece, which lost a quarter of its national output during a decades-long financial crisis, expects to see its economy shrink by 8.2% this year.