The prime minister told reporters that the second wave of the coronavirus pandemic in the country is not over yet.
"We will introduce a curfew from 15 December, but it will be stricter. It will be in effect from 20.00, not from 21.00, as mentioned earlier," he said.
Castex added that there would be no curfew exceptions on New Year's Eve. At the moment, France is on a plateau, the number of new infections is no longer falling, but slightly increasing over recent days, he said.
Cultural institutions, including museums, cinemas, theatres, which the French authorities had expected to open from 15 December, will remain closed for at least three more weeks, according to Castex.
The current stay-at-home state order at a national level came into effect on 30 October, and the government announced its three-stage lockdown relief strategy for next month. To date, national health authorities have confirmed 2,337,966 COVID-19 cases, 56,940 related fatalities and 174,658 recoveries.