An additional 99 people have tested positive for coronavirus on a cruise ship off the Japan coast, Japanese media said Monday, citing new figures from the health ministry.

That would take the total number of positive cases on the Diamond Princess to 454. The health ministry declined to confirm the reports immediately.

It was also not clear whether the figures included 14 US citizens who tested positive for the virus but were allowed to board evacuation flights home.

The Diamond Princess vessel moored in Yokohama near Tokyo has become the second-largest cluster of coronavirus cases outside the epicentre in China.

Passengers have been largely confined to quarters since February 5 with only brief and occasional breaks to take air on deck -- with face masks.

The quarantine period is over on Wednesday but many countries have decided to repatriate their citizens after an alarming climb in cases on board.

The US was the first country to evacuate its citizens from the ship but Australia, Canada, Italy and Hong Kong have indicated they will follow suit.

On land, cases in Japan have risen to 65, with authorities warning that the outbreak is entering a "new phase" and advising people to avoid large gatherings.

A public celebration of the new emperor's birthday on Sunday has been scrapped and organisers of the Tokyo Marathon scheduled on March 1 are reportedly considering cancelling the amateur part of the race.