The labour ministry said on Tuesday the new arrangement would apply to all shared spaces in offices and factories, but would not extend to individual offices where only one employee is present.

It also said that working from home would remain its recommended option for employees. A government official said masks at work would become mandatory from Sept. 1.

He further said there would be talks with employers and unions about borderline cases, such as when only two people are present in one large open-space and sitting well apart.

Details will also be worked out for special work environments such as frozen food warehouses, where masks are not practical as they would freeze.

Mask-wearing is also compulsory nationwide on all public transport and in most indoor public spaces such as shops and museums, as well as in crowded outdoor areas in some cities.

France imposed some of Europe's toughest lockdown restrictions earlier this year, greatly reducing the rate of coronavirus infections. But in the past few weeks the numbers of new COVID-19 cases have climbed, and public health officials have warned that contagion could spin out of control.

The government has been under pressure from trade unions to step up protective measures in time for September, when people return to work after long summer holidays, and when children are due back at school.

"The best thing we can do to prepare for the return from vacations is to reassure employees that, together, we are taking the precautions to avoid spreading the virus," Elisabeth Borne, the labour minister, was quoted as saying by the ministry.