Paris, Aug 28 (IANS): French Prime Minister Jean Castex declared an additional 19 departments, including the Paris region, high-risk zones as "the virus is progressing throughout the territory," forcing authorities to toughen rules and consider all scenarios to contain an eventual second wave of coronavirus cases.

The government already classified Paris and the Bouches-du-Rhone area around Marseille as red zones for coronavirus cases on August 14.

At a news briefing on Thursday, Castex warned that France was witnessing "a phase of resurgence of the epidemic", in the wake of the strict confinement imposed between March 17 and May 11, Xinhua news agency reported.

In the red zones where the virus is actively circulating, the vigilance threshold, which indicates the number of infected people per 100,000 inhabitants, exceeds 50 patients, well above the limit of 10, Castex said.

The COVID-19 reproduction (R) number is now 1.4, up from 0.77 per cent in June when France returned to normalcy. This means that 10 infected people will infect an additional 14 on average.

In the coronavirus high risk zones, the authorities have the power to impose localized confinement by limiting travel, restricting public transport and closing non-essential businesses.

A further 5,429 patients tested positive for COVID-19 on Wednesday, the highest daily spike in four months, the country's Public Health Public Agency said.

A total of 253,587 cases have now been confirmed, while 340 clusters are still active, up by 27 in one day, it added.

Citing the deteriorating sanitary indicators, Castex stressed that the government had to intervene fast to control an eventual new outbreak, which French scientists say may overwhelm the country's health system this autumn-winter.

"The epidemic can grow exponentially if we do not react now", he said.

"The rule is simple: wearing a mask is now compulsory in all closed spaces where several people gather," he added.

Teachers in kindergartens, schools, colleges and universities as well as students older than 10 years are now required to wear mask.

Furthermore, the wearing of face masks would also be mandatory on the streets of Paris and the neighboring cities, which make up the country's most populated region. The same rule has already been imposed in Marseille and Toulouse.

As part of its prevention plan, the government also aims to bolster the testing capacity to one million tests per week in September from 830,000 currently.

"Our first weapon to fight against the spread of the virus is prevention," Castex told reporters, adding that the government was considering "all the scenarios" in case of a new outbreak.

"Territorial or nationwide lockdown plans are ready. Our health system is also ready for a new wave of patients. But our objective is to do everything to avoid a new general re-confinement," the prime minister said.

"The more activity stops, the more the economic and social crisis increases, the more dramatic the human consequences will be," he said.