Face masks must be worn everywhere in Paris from Friday morning in order to curb a surge in coronavirus infections, french police said on Thursday.

The measure applies to all pedestrians as well as cyclists in Paris and its suburbs, a densely populated area with a total population of nearly seven million people.

Motorists will not have to wear a mask inside their car.

According to a statement from the Paris police prefecture, the deterioration of the health situation in the country has led the prefect to take this strong measure in the interest of the population.

Earlier on the same day, Prime Minister Jean Castex said the government would order the mandatory wearing of masks across Paris but he did not give a deadline or specify the area.

"The virus is spreading all over the country... The spread of the epidemic could become exponential if we do not react quickly,” he said.

The reproduction "R” number of infections in France has risen to 1.4, Castex said, meaning that every 10 people with the virus will infect another 14. 

According to epidemiologists, an R number above 1 can lead to exponential growth.

Castex, who oversaw France’s emergence from lockdown before his appointment as premier in July, has said life must go on but that France will not let down its guard as scientific advisers warn of a second wave hitting in the autumn.

Reports indicate that France reported 5,429 new daily infections on Wednesday, a new post-lockdown high and a level not seen since the height of the epidemic in early April.

Infections were rocketing among young people, Castex said, as he urged grandparents not to pick up their grandchildren from school when the academic year begins on Sept. 1.