SYDNEY (AFP) -- Two Australians evacuated from the Diamond Princess cruise ship have tested positive for coronavirus, authorities said Friday, raising questions about Japan's policy of allowing evacuees to return home after testing negative.

"We have two people who are positive for the COVID-19 virus. Those two people have mild illness," said Dianne Stephens, acting chief health officer for the Northern Territories.

Hundreds of people have been allowed to leave the ship after testing negative for the disease and many have returned to their home countries to face further quarantine.

Some 164 Australians aboard the Diamond Princess were cleared for transfer from the ship to quarantine in Australia's remote north earlier this week.

But hundreds of Japanese passengers were cleared and warned only to "stay at home unless absolutely necessary," and to "never use public" transport and use a mask if they do venture out.

A total of six Australian evacuees have now been retested and the two -- described as "an older person" and "a younger person" -- tested positive.

Australia's Chief Medical Officer Professor Brendan Murphy said the public should not be concerned.

"I just want to reassure the community that whilst this is another two cases in Australia, it's a first for some time now. These were expected and we're well-placed to manage them," he said.

Fifteen previous cases of coronavirus had been linked to the outbreak of the disease in China.

Murphy also expressed confidence that Japan and South Korea -- where the number of infections nearly doubled Thursday to 104 -- would be able to contain the disease.

"Both Japan and South Korea have well-developed health systems. And I would certainly be confident that they will be onto identifying those cases and tracing contacts," he said.

"But it is obviously a concern that any country where there is significant further transmission." (AFP)