Among the cases was a junior high school teacher in Chiba prefecture east of Tokyo, who went to work even though she had symptoms, raising fears the virus could spread among her students and co-workers.

In the northern prefecture of Hokkaido, a boy less than 10 years old was added to the list. On Friday, two brothers in an elementary school in Hokkaido were confirmed infected.

Children had been thought to possibly be less vulnerable to the new virus, with far fewer reported infections in much younger people.

Japan's government is facing growing questions about whether it is doing enough to stop the spread of the coronavirus as Tokyo prepares to host the 2020 Summer Olympics in July.

In Japan, more than 100 people have now tested positive for the flu-like illness, which has killed more than 2,300 in mainland China, where it emerged in the central Chinese city of Wuhan late last year.

In addition, more than 600 cases have also been reported on the Diamond Princess cruise ship that has been quarantined off Yokohama for more than two weeks.

Passengers who are not ill continued to leave the ship on Saturday, media reported, but uncertainty is high due to concerns that quarantine procedures on the ship were not adequate.

Of the new cases reported on Saturday, eight were in Hokkaido, two were in Chiba prefecture, one was in Tokyo, and another in Wakayama prefecture in western Japan.

Two more cases, a man in his 60s and a man in his 50s, were also confirmed in Kumamoto prefecture in southern Japan.

The junior high school teacher in Chiba, in her 60s, first showed symptoms on February 12 and was hospitalised on February 19. She went to work while she had symptoms, so the local government will close her school for two days from February 25.

Australian Associated Press