Live updates: follow the latest news on Covid-19 variant Omicron
France became the sixth country in the world to report more than 10 million Covid-19 infections since the outbreak of the pandemic, according to official data published on Saturday.
French health authorities reported 219,126 new confirmed cases in a 24-hour period, the fourth day in a row that the country has recorded more than 200,000 cases.
France joined the United States, India, Brazil, Britain and Russia in having had more than 10 million cases.
Saturday's figure was the second highest after the 232,200 record on Friday when French President Emmanuel Macron warned the next few weeks would be difficult.
In his New Year's Eve address, Mr Macron did not mention a need for more restrictive health measures than those already announced, adding that the government should refrain from further limiting individual freedoms.
But the government said earlier on Saturday that from Monday wearing masks in public spaces would be mandatory for children as young as six versus 11 before.
And some big cities, including Paris and Lyon, have re-imposed wearing of masks in the street for everyone.
French Health Minister Olivier Veran said on Sunday the isolation period for fully vaccinated people who test positive for Covid-19 would be cut to seven days from 10 days.
French authorities followed other countries such as the United States, which this week cut the isolation period to prevent disruptions in industries for lack of staff.
"This isolation could be lifted after five days in case of a negative test," said Mr Veran.
"Those who are not vaccinated will have to self-isolate for 10 days, with a possibility to come out of isolation after seven days under the same terms," Mr Veran told newspaper Le Journal du Dimanche published on Sunday.
He also said the new Covid-19 Omicron variant was too contagious to be stopped unless a "strict lockdown" was re-imposed.
The seven-day moving average of new cases in France, which smoothes out daily reporting irregularities, rose to an all-time high of 157,651 on Saturday - jumping almost five-fold in a month.
The number of people requiring hospital treatment for Covid-19 has increased by 96 over 24 hours, standing at a more than seven-month peak of 18,811. But that figure is still almost half the record 33,497 reached in November 2020.
The Covid-19 death toll increased by 110 over 24 hours to 123,851, the 12th highest globally.
The seven-day moving average of new daily deaths has reached 186, a high since May 14.