About 200 Australians on the coronavirus-hit cruise ship in Japan will be flown to Darwin on Wednesday where they will be quarantined for two weeks.

About 200 Australians on a coronavirus-hit cruise ship in Japan will be evacuated on Wednesday to an unused workers camp near Darwin for a fresh two-week quarantine period.

Passengers have been stranded on the Diamond Princess cruise ship for more than a fortnight.

Seventy more people on board were confirmed to have the virus on Sunday, bringing the number of cases from the ship to 355, including 16 Australians.

Those who tested positive for the virus are being treated onshore in Japan.

Prime Minister Scott Morrison said Qantas had offered its aircraft for the flight and Australians wouldn't have to pay to return home.

"For those who are onboard, we are with you, we are doing everything we can to support you," he told reporters in Melbourne on Monday.

Mr Morrison ruled out Christmas Island as a quarantine location as many of the evacuees were older in age and needed to be close to a major hospital.

Vera Koslova-Fu, a Melbourne woman stuck on the ship, has questioned whether people would take up the evacuation offer in the hope they can leave the ship as early as Friday, when their existing quarantine period expires.

But Australia's chief medical officer Brendan Murphy said experts were unable to pinpoint why the number of cases onboard the ship had continued to rise.

"Given there has been recent cases, we cannot be absolutely sure that any of the currently-well people on the ship who are coming home on Wednesday are not carrying the virus," he said.

"We cannot be sure. And if we cannot be sure we have to take precautions."

Wednesday's flight will also include New Zealanders, who will be transferred home after landing in Darwin.

Americans on board the Diamond Princess were being flown to the US on chartered planes from Sunday, while authorities in Canada, South Korea, Hong Kong and Italy have announced flights home for their citizens.

The Australians on board must pass a coronavirus test before they can be brought home, and elderly people will be given priority in the evacuation.

They will join another few hundred Australians in the midst of their two-week quarantine period at the disused work camp near Darwin.

They were evacuated from the coronavirus epicentre of Wuhan in China and landed in Australia on February 9, with their quarantine period set to end on Saturday.

There are now more than 69,200 cases of COVID-19 worldwide, with 1670 reported deaths.

There have been 15 cases in Australia, with eight people now recovered and the rest in a stable condition.

Meanwhile, the first Australians to be quarantined on Christmas Island over the coronavirus have landed back on the mainland.

Two aircraft refuelled at Port Hedland in Western Australia on Monday afternoon.

One of the aircraft will continue on to Sydney and Canberra while the second will go to Adelaide and Melbourne.

A third flight will travel via Perth and Brisbane, leaving about 35 people on the island for another flight on Wednesday.

None of the people will be required to take further tests when they get home, as they were cleared just before they left the island.