Schoolchildren in large parts of France were ordered Monday to again wear face masks in class, less than a month after being allowed to remove them, as the country tries to tamp down a surge in Covid cases.

Primary schools in 40 of France's 101 departments or administrative areas, which had been mask-free for weeks, are affected by the order, which comes a day before President Emmanuel Macron addresses the nation about the health crisis.

Under the government's Covid protocol, primary school pupils have to wear masks when the incidence rate rises above 50 new infections per 100,000 inhabitants over five consecutive days.

With nearly 75 percent of the population inoculated against the coronavirus, France is one of Europe's vaccine leaders.

But the pace of new vaccinations has slowed since the summer, when millions rushed to get shots after the introduction of a Covid pass to enter bars, restaurants, gyms and other entertainment and sporting venues.

The latest government edict brings to 61 the number of departments where schoolchildren have to cover their noses and mouths. 

They include the areas surrounding Paris as well as the southern city of Marseille.

In secondary schools, masks remain compulsory irrespective of the number of Covid cases.

On Tuesday evening, Macron will address the nation about the health crisis for the first time since July 12.

He is expected to discuss the booster shot campaign currently underway among over-65s and those with underlying health conditions. 

So far only half of those eligible for a top-up shot have received the jab.

Prime Minister Jean Castex told AFP on Friday that the government was considering updating the Covid pass to include a mandatory booster shot.

The World Health Organization has expressed "grave concern" over soaring Covid cases in Europe, warning that the continent could see another half a million deaths by early next year.

Germany last week set a new record for daily cases, with nearly 34,000 new cases over the previous 24 hours. 

France, by comparison, has been spared a steep rise in infections, with health authorities reporting 8,547 new cases between Saturday and Sunday.

In the absence of a fourth wave of infections, many parents and teachers have expressed dismay over the reimposed restrictions on younger children.

The secretary general of France's biggest primary teachers union, the SNUIPP-FSU, warned that the "yo-yo effect" would have a detrimental effect on students.

"This to-ing and fro-ing risks creating a sense of instability in schools," Guislaine David said.

Education Minister Jean-Michel Blanquer told France Info radio that while the new mask mandate was "unpleasant" it was "necessary".