A new variant of the coronavirus that was first detected in South Africa has been confirmed in Japan.

On Monday, the health ministry said it was found in a woman in her 30s who arrived at Narita Airport near Tokyo on December 19. She traveled from South Africa.

Japan's health ministry says it has confirmed the country's eighth case of infection with a new strain of the coronavirus.

The ministry says a Tokyo resident in her 50s tested positive for the variant on Sunday.

Medical experts say a surge in new coronavirus cases in Tokyo is starting to overstretch its healthcare system, making it very difficult to provide care for other patients.

The warning came when an advisory panel of infectious disease and public health experts met Tokyo Metropolitan Government officials on Thursday for a weekly assessment of the coronavirus situation.

An NHK survey shows the Japanese prefecture of Okinawa has the nation's highest number of confirmed coronavirus cases per 100,000 people in the preceding seven days. Officials of the southern island prefecture warn the local medical system remains under strain.

The survey put the figure for Okinawa at about 18 as of Saturday, followed by Tokyo at 16, Fukuoka and Osaka prefectures at 14, and Aichi Prefecture at 13.