Rottnest Island off Perth will be a coronavirus quarantine zone for 800 Australians

Rottnest Island off Perth will be a coronavirus quarantine zone for 800 Australians onboard the Vasco da Gama, as the number of confirmed cases from other cruise ships continue to rise.

Premier Mark McGowan says Fremantle is the final port of call for the vessel and is due to arrive on Friday, carrying 950 passengers and 550 crew.

All crew and foreign nationals, including 109 New Zealanders, will remain onboard until arrangements are made to fly them out of the country.

But 800 Australians, including 200 West Australians, will be immediately transferred to Rottnest for 14 days of isolation.

The island, usually a holiday hotspot, has been cleared of visitors.

"I'm not going to take any chances on this issue," Mr McGowan told reporters on Wednesday.

Another cruise ship, the Artania, which was due to arrive at Fremantle for refuelling only, has about 25 passengers and crew with respiratory symptoms onboard.

"I also understand one passenger, who is no longer on the ship, tested positive with COVID-19," Mr McGowan said.

There are more than 800 foreign passengers and 500 crew onboard, and the ship has requested assistance, which WA health officials are delivering.

Meanwhile, the Magnifica departed Fremantle on Tuesday after all passengers and crew were kept onboard during refuelling but was told overnight it could not dock in Dubai, so headed back.

Both the Magnifica and Artania must remain at anchor off the coast, and nobody will be allowed to disembark unless they have a life-threatening emergency.

"There are no circumstances where we will allow passengers or crew to wander the streets in our state," Mr McGowan said.

He has asked the Commonwealth for immediate assistance with both anchored ships to ensure they do not try to declare an emergency to disembark.

The number of coronavirus cases in the state has surged by 30, bringing the total to 205, including five from cruise ships and eight in regional WA.

Health minister Roger Cook said WA had recorded 47 cases from cruise ships in total so far.

Mr Cook announced police would be included with health workers in the COVID-19 testing regime.

Cruise ship passengers with symptoms, who disembarked in the past 14 days, will also be tested.

Vulnerable people and those in high risk settings such as aged care, Aboriginal communities, detention centres, boarding schools and military barracks will be tested if there are two or more people with respiratory illness.

Testing will also be done where there are outbreaks in workplaces.

Police Commissioner Chris Dawson said 90 vehicles had crossed the state border before the closure.

WA has become the first state to restrict takeaway alcohol sales for at least two weeks, in a effort to prevent the healthcare system from being overburdened.

Mr Dawson said it was not prohibition, given people could buy more than 100 standard drinks a day.

Australian Associated Press