Moscow Mayor Sergei Sobyanin on Friday ordered older people to stay at home and recommended employers ramp up remote working after a spike in coronavirus infections.
The COVID-19 caseload in Russia, the world's fourth most affected country, had remained steady for several months but in recent days climbed steeply towards levels last seen in June.
Health officials later said pregnant women and those who have recently given birth should also stay at home.
The mayor highlighted a "serious" increase in hospital admissions and said over-65s and those with chronic illnesses should stay at home from Monday and shop rarely, although walks outside would remain unrestricted.
"Unfortunately we see a significant increase in the number of confirmed cases in Moscow in recent days," Sobyanin wrote in his blog.
"So from September 28, we are asking you to stay at home."
The move prompted a mixed reaction from Muscovites facing confinement.
"What happens, happens. I can't stay at home, it's physically impossible," said Boris, a fit-looking 84-year-old. "I'm not afraid. I've lived long enough."
But 81-year-old Lyudmila Ivanovna, a retired engineer in mask and gloves, backed the measure, saying she had neighbours who had caught the virus.
"We'll stay at home," she said. "People have to understand that their own health and that of their loved ones is their own responsibility."
New coronavirus cases in Moscow on Friday reached 1,560—the highest level since June 12—and nearly 800 people have been taken to hospital in the past 24 hours.
Russia has confirmed over 1.1 million coronavirus cases and 20,056 deaths.
On Friday, it announced 7,212 new cases, the highest number since June 23.
Beyond the capital, the highest number of new infections are in the region surrounding Moscow and in the second largest city of Saint Petersburg.
President Vladimir Putin on Thursday in comments to newly elected governors warned that "if we relax, the situation could change drastically".
"You mustn't let these problems drift into the background, otherwise they will blaze up again with new force," he said.
The Moscow mayor's decree presents the stay-at-home measure as a compulsory rule, with exceptions for medical care, shopping, walking dogs and commuting to work.
At the beginning of the virus lockdown in late March, Sobyanin brought in some of the country's strictest measures including cancelling free travel passes for older people to discourage unnecessary trips.
He said Friday that he was not repeating this step and had asked police not to fine rule-breakers.
'Not conquered yet'
Sobyanin said those in high-risk groups should work from home or claim vacation or sick leave if possible.
He warned that as winter approaches, older people and those with chronic illnesses were at risk of catching a cold and the virus at the same time.
He also told employers: "I firmly ask and recommend you to move as many of your staff as possible to home-working."
Doing this in spring saved "thousands of lives," he said, also urging workplaces to carry out temperature checks and virus tests.
Warning the virus was "not conquered yet", he called for Moscow residents to wear face masks and gloves on public transport and in shops, a rule already in place but widely flouted.
Officials in the capital have recently ordered several supermarkets to close for failing to enforce the rules.
On Friday, an official said the city had fined a luxury department store, TsUM, more than 1 million rubles ($13,000).
At the peak of lockdown in May, Sobyanin ruled that residents could only go out to their nearest shop or to walk a dog, while those making journeys needed electronic passes.
"We all really don't want to go back to the harsh restrictions of spring," the mayor said. "I hope we can avoid this."
Russia has boasted of creating the world's first approved coronavirus vaccine, Sputnik V, although it is still undergoing clinical trials.
Putin praised the vaccine as safe and effective during a speech to the United Nations on Tuesday.
A number of high-profile officials and politicians have already taken the vaccine, and Putin has said one of his daughters was vaccinated.
© 2020 AFP