Some 20 million French people are preparing to spend their first evening under curfew on Saturday, a measure taken by the government after an alarming surge in new coronavirus cases.

The 9:00 pm to 6:00 am curfew came into force at midnight on Friday in the Paris region and eight other large cities, affecting nearly a third of the country's population.

People will need a certificate for permitted activities, such as travel to or from work, for medical attention, to visit a dependent relative or to walk a dog.

Those who do not comply risk a fine of 135 euros ($160), while repeat offenders could face fines of up to 3,750 euros ($4,400). 

Some 12,000 police officers and gendarmes, in addition to municipal police teams, will be deployed to enforce the curfew.

Restaurant owners, for whom the second part of the evening represents an important part of turnover, have complained about the measure.

"Closing at 9:00 pm will have no effect (on the epidemic). They're not attacking it in the right way," said Gerard, the manager of a Toulouse restaurant.

The government has defended the measure as the only way to avoid a lockdown, at a time when indicators assessing the coronavirus epidemic, such as deaths and hospitalisations, are deteriorating across Europe.

French health authorities on Friday recorded more than 25,00 new coronavirus cases, with 178 deaths.

The curfew measure, which comes just ahead of a two-week school holiday, contains no travel restrictions, raising the prospect that huge numbers of families will flee cities for the country.

Scheduled to last at least four weeks, the curfew could be extended if the epidemic does not show signs of abating. President Emmanuel Macron has already mentioned the date of December 1.