Wearing a face mask will be compulsory in busy parts of Paris from Monday amid a rise in coronavirus infections in and around the French capital.
Police said the order would apply to people aged 11 and over in “certain very crowded zones”.
The virus had been circulating more widely in the region since mid-July, they said. Face masks are already compulsory in enclosed public spaces.
Experts have warned that France could lose control of Covid-19 “at any time”.
Several cities, such as Nice and Lille, have introduced their own additional orders making mask-wearing mandatory in certain outdoor areas.
Paris authorities have not yet detailed which areas will be affected by the new order, which will come into force at 08:00 (06:00 GMT) on Monday.
The zones where masks are mandatory will be evaluated on a regular basis, they said.
In a statement on Saturday, authorities said the rate of positive coronavirus tests was 2.4% in the greater Paris area, compared to the national average of 1.6%.
They added that 400 people were testing positive for coronavirus every day in the region, with those aged between 20 and 30 particularly affected.
Officials earlier this week said they had called for new measures on masks in the French capital.
“We are going to ask that [mask-wearing] become compulsory in crowded outdoor places and where respecting a metre’s distance between people is difficult,” said Anne Souyris, the deputy mayor in charge of health.
The new order comes after the government’s scientific advisers warned on Tuesday that France could lose control of the virus “at any time”.
France reported 2,288 new coronavirus infections in its daily figures on Friday, marking a new post-lockdown high.
In total, the country has recorded more than 235,000 cases of coronavirus and more than 30,000 deaths, according to data collated by Johns Hopkins University.