France said Wednesday it would allow in flights from ten southern African countries from Saturday, but with "drastic" restrictions permitting only French and EU residents to disembark, along with diplomats and flight crews.

These travellers must have a Covid test upon arrival, with a negative result still requiring a seven-day quarantine, while a positive test will prompt a 10-day quarantine, government spokesman Gabriel Attal said after a cabinet meeting.

France is one of several countries worldwide that halted flights from southern Africa in recent days after the more contagious Omicron strain of coronavirus was reported by South Africa.

But the World Health Organization warned Tuesday that "blanket" travel bans risked doing more harm than good, by potentially dissuading countries from sharing data about the evolving virus.

Attal said French authorities had discovered 13 suspected Omicron cases so far that were under analysis for confirmation.

"Let's not be fooled or naive, there will very probably be cases on our territory in the coming hours or days," he said.

Attal also announced that all travellers arriving from outside the European Union would have to present a negative Covid test less than 48 hours old, in a bid to halt the spread of the more contagious Omicron variant.

In addition, non-vaccinated travellers from within the EU will have to show a negative test less than 24 hours old.