Travellers from countries where the infection rate is deemed to be high will be subject to compulsory testing on arrival at French airports and sea ports, Castex told reporters during a visit to Charles-de-Gaulle international airport, north of Paris.
The tests will apply to “French citizens who live in these countries or citizens of these countries with an established residence in France” who will be the only ones allowed to enter, the prime minister added.
France does not allow general travel to and from these countries, which include the United States and Brazil.
Travellers who test positive will be required to spend 14 days in isolation to prevent the spread of the virus.
Castex said some of the high-risk countries already require airline passengers to show a negative virus test before boarding. It was not clear if they would be re-tested upon arrival in France.
He also did not specify if people would have to wait for their test results before being allowed to leave the airport.
Along with the United States and Brazil, which are reporting tens of thousands of new cases each day, the countries include Algeria, Bahrain, Israel, India, South Africa, Kuwait, Qatar, the United Arab Emirates, Oman, Panama, Peru, Serbia, Turkey and Madagascar.
Morocco, which has reported rising cases in recent weeks, is not on the list for now but could be added later, an official in the prime minister’s office said.
Coronavirus tests will be rolled out across France by August 1, and will also be carried out at French ports, Castex said.
The new measures come amid signs that the rate of infection is accelerating again in France more than two months into the country’s gradual exit from lockdown.
On Friday, the health ministry said the number of confirmed cases had risen by 1,130 over 24 hours. It was the second consecutive day that new cases exceeded 1,000.
The ministry, in a statement, said the figures showed the need for people not to lower their guard while the virus continues to circulate.
“We have cancelled out much of the progress accomplished during the first weeks of exit from lockdown,” the ministry said, citing reports that some people who test positive for the virus fail to self-isolate.
French authorities are also concerned about a spike in infections in neighbouring Catalonia, with Castex on Friday warning French citizens not to travel to the Spanish region.
“Concerning the situation in Catatonia, which is displaying worsened indicators for infection, we strongly encourage French citizens to avoid going there until the health situation improves,” Castex said.
Regional authorities across Spain introduced fresh coronavirus restrictions on Thursday aimed at stamping out a surge in infections. France had said last weekend it had not ruled out closing the border between the two countries.
In Catalonia, nearly 8,000 cases were diagnosed in the 14 days up to Thursday almost half of the 16,410 detected throughout the country – despite guidelines for residents of regional capital Barcelona to stay at home.
Castex also said Paris was in discussions with the government in Madrid to limit flows of traffic from Spain into France as much as possible.