"The second wave is now under way", he said, shortly before the country announced a record 41,622 new cases, the BBC reported.
In these regions, curfews from 9 p.m.to 6 a.m. will take effect from Friday midnight and last six weeks, said Castex at a press conference.
"There has been a perception in recent months that a second wave does not exist, or that it is a small wave". By mid-October the seven-day average of daily cases was at 20,000 and is now nearly 30,000.
The number of people in hospital with COVID-19 jumped by 976 to 15,008, the biggest one-day increase since early April, while the number of people in intensive care rose by 122 to 2,441.
The weekly pace of infections has been rising for 20 days. Mr Castex said police had issued 4,777 fines.
In just one week, the infection rate per 100,000 people has climbed by 40%, he said. "The coming weeks will be tough".
"But in the same way, I can say that the French economy will see a strong rebound in 2021" and that growth will return to 2019 levels in 2022, the minister said.
None of these cities was concerned by the first curfew regulations.
The southern coast, from the Pyrenees to Nice, is to go under curfew, along with a mass of areas in the southeast and central France, as well as patches in the north, in the east and around Paris.
Daily virus cases are hitting records around Europe, including new highs in the Netherlands and Greece. When ready, it will replace the failed StopCovid app, which the prime minister recently admitted he had never downloaded.
France has reported over 34,000 virus-related deaths, one of the highest tolls in Europe.