President Emmanuel Macron took the decision to bring patients to the French mainland to relieve the Ajaccio hospital's emergency care unit and enable it to "anticipate the hospitalisation needs of the most seriously ill patients," the island administration said.

Corsica has a population of about 340,000, of which some 90,000 are older than 60 -- the age group most at risk of serious health problems as a result of coronavirus infection.

By Thursday, the island counted 164 confirmed infections and seven coronavirus deaths.

Most of those infected lived in the capital, which has 15 beds reserved for critical care, to be augmented to 26 shortly.

About a dozen critically ill patients will be taken from Ajaccio to hospitals in France's southern Cote d'Azur region, Corsican administrator Franck Robine told AFP, adding that officials expected a sharp increase in new cases in the coming days.

The naval ship, Tonnerre, has a fully-equipped hospital on board, with 69 beds.

Earlier this week, the French military evacuated six patients from Mulhouse, an infection hotspot in the east of France, to the larger cities of Marseille and Toulon in the south.