France was preparing Wednesday for tough new restrictions to halt a flare-up in Covid-19 cases that has alarmed doctors, with a second lockdown widely mooted as hospitals battle an influx of patients.

President Emmanuel Macron is to announce more measures in a televised address to the nation Wednesday evening, a day after officials announced coronavirus 523 deaths in 24 hours -- the highest daily toll since April.

Macron will hold another crisis meeting with top ministers before his announcements, which a government official said were likely to be "unpopular."

France's main newspapers and several radio stations cited various unnamed sources saying Macron had become convinced of the need for a nationwide four-week lockdown, which would be voted on in parliament on Thursday.

The head of Macron's LREM party, Stanislas Guerini, appeared to be preparing the ground for a shutdown when he told France 2 television that the nation needed "strong measures, powerful measures that are understandable for all French people, and probably at a national level".

The prospect sent French stocks sharply lower, with the bellwether CAC-40 index slumping 2.4 percent at midday.

By Tuesday, there were 2,918 coronavirus patients in intensive care in France, more than half the capacity of 5,800 beds. 

Nearly 19,000 were in hospital overall and France recorded over 33,400 new positive tests in 24 hours, with some hospitals left with no choice but to start transferring patients to less-crowded facilities.

France's death toll now stands at 35,541.

At the height of the epidemic in March and April, France erected field hospitals and had to evacuate hundreds of patients from hospitals in hard-hit zones to less burdened areas, including some to Germany, Switzerland, Luxembourg and Austria.

'Difficult decisions' 

The government has been loath to impose a new lockdown that would pummel the economy afresh, and business chiefs have warned a total shutdown would force another wave of layoffs and bankruptcies.

Instead, the authorities imposed a curfew for Paris and other cities two weeks ago that requires about 46 million people -- two-thirds of the population -- to be home from 9:00 pm to 6:00 am.

Health Minister Olivier Veran had said it would take two to three weeks to see if the curfews were working, but a surge in new cases since then has forced the government to scramble for new measures.

Other options said to be considered by Macron included extending the curfew hours, possibly with a full lockdown on weekends, or targeted stay-at-home orders for hardest-hit regions.

Another option could be to postpone the return of students from the autumn holiday that ends this weekend, in particular to high schools and universities.

"We have to prepare for difficult decisions," Interior Minister Gerald Darmanin said Tuesday.

Frederic Valletoux, head of the Hospital Federation of France, said Wednesday a full lockdown was needed to stop the second epidemic wave "devastating" the hospital system.

"The lockdown has not yielded all the results we had hoped for, we must draw conclusions very quickly and take radical measures," he told France inter.

Philippe Juvin, the head of emergency services at the Georges-Pompidou hospital in Paris, agreed that a lockdown was inevitable.

He pointed to a "high rate of uptake of intensive care beds and a risk, without strong measures, of the health system being submerged."

France's public accounts minister Olivier Dussopt, meanwhile, said every month of generalised lockdown would cost the economy between two and 2.5 points of GDP.

"This represents more than 10 billion euros ($11.7 billion) in intervention spending and at least 10 billion euros in lost tax revenue," he told Sud Radio.