France reported record 52,010 cases of Covid Sunday, as infections rise rapidly.
Pandemic adviser warned true total is likely above 100,000 as second wave hits.
While increased testing is in-part to blame for rise, Jean-Francois Delfraissy said he is shocked by 'brutality' of second wave that 'will be stronger than the first'.
Record cases also logged in Germany, Russia and Italy as Europe suffers.
France is probably seeing more than 100,000 coronavirus infections per day, the government's chief pandemic adviser has admitted, as the official toll hit a record 52,000 cases on Sunday.
Jean-Francois Delfraissy, who leads France's Scientific Council, said he has been shocked by the 'brutality' of the second wave that is currently hitting Europe.
Once asymptomatic cases and people who are not getting tested are taken into account, he said, France's daily case total is probably in six figures.
While increased testing is in part to blame for the record-breaking rises, Delfraissy added that the second wave of virus 'will surely be stronger than the first.'
France has seen its daily coronavirus case totals rise rapidly in recent weeks, almost doubling from 29,837 a week ago on Sunday, to 52,010 reported this Sunday.
While deaths have not risen as rapidly, half of the country's intensive care beds are now occupied with coronavirus patients, with more than 2,500 in use.
In the Ile-de-France region, where hard-hit Paris is located, that figure rises to two thirds of intensive care beds.
If the numbers continue to rise then the health system risks being overwhelmed, meaning deaths could soar as both Covid and non-Covid patients struggle to access emergency treatment.
Mr Delfraissy described the situation in France as 'very difficult, even critical,' adding that 'we have a virus that circulates extremely quickly'.
Asked what can be done to stem the rise in cases, Delfraissy suggested extending 9pm til 6am curfews that currently cover around two thirds of France's population to the whole country.
He also suggested a 'circuit breaker' lockdown of the kind being used in Ireland, Wales and Scotland in the hope of rapidly decreasing cases.
In France, Delfraissy suggested the lockdown would be for a short period of time and would still allow children to go to school.
Exiting the lockdown would also be more orderly than it was earlier in the year, he said, with a return to curfew - not the 'new normal' that was previously proposed.
Meanwhile Dr. Eric Caumes, head of the infectious and tropical diseases department at Paris' Pitie-Salpetriere Hospital, warned that 'we have lost control of the epidemic.'
He said the breaking point came 'a couple of weeks ago' and that the country is rapidly heading towards another full lockdown.
Caumes described the curfew system as a 'risky bet', saying its effectiveness at reducing infections is unknown.
It will take 10 to 15 days to assess whether it has had an impact, he said, and if it fails then France will have 'no choice' but to return to lockdown.
'If it is not efficient at all, we will have to confine, there will be no other solutions unfortunately,' he told FranceTVInfo.
Most major European countries are now reporting daily record coronavirus totals, which are accelerating rapidly even when increased testing is taken into account.
Governments have been desperate to avoid the lockdowns which curbed the disease at the start of the year at the cost of shutting down their entire economies.
But the steady rise in new cases has forced them to ratchet up controls.
'We are facing very, very difficult months ahead,' German Chancellor Angela Merkel told a meeting of leaders from her Christian Democrat party, according to Bild.
Although Germany has fared relatively well compared to other countries in Europe, it too has seen a sharp rise in cases and the closely watched Ifo business climate index fell on Monday, reflecting the worries over the virus.
The gloom around the resurgent virus weighed on financial markets, where oil prices dropped on concerns of another slide in demand and stock markets also fell.
In Spain, which has had more than 1 million cases of the disease, Prime Minister Pedro Sanchez warned the country was facing an 'extreme' situation as he announced a new state of emergency on Sunday, imposing local nighttime curfews and banning travel between regions in some cases.
Italy, the country worst hit in the early stages of the crisis in March, also imposed new curbs, ordering restaurants and bars to close from 6 p.m. and shutting down cinemas, and gyms and imposing local curfews in several regions.
Street clashes with small groups of protestors over the weekend and angry criticism from restaurant owners and business groups about the impact of the measures underlined the increasingly tense climate facing Prime Minister Giuseppe Conte.