Western Australia will close its border in coming days and Rottnest Island may be turned into a COVID-19 quarantine zone, Premier Mark McGowan has announced.
Mr McGowan says entry to WA would be restricted via road, rail, air and sea from 1.30pm local time on Tuesday.
There will be exemptions for health, emergency, defence and policing personnel, certain mining industry workers, flight crews and those delivering essential goods via ports and trucks.
Exemptions will also be granted on compassionate grounds and where people live near border communities.
Unless exempted, arrivals from interstate will be ordered to self-isolate for 14 days.
"These are extreme steps but these are extreme days," Mr McGowan said on Sunday, as 30 new cases were confirmed, bringing the state's total to 120.
He told people planning to holiday in WA to cancel their plans.
Travel within the state is still being allowed for now, excluding remote Aboriginal communities, "but that may change".
Critical mining, and oil and gas operations will continue, with about 2500 resources sector workers continuing to travel to WA from interstate.
Chamber of Minerals and Energy WA chief executive Paul Everingham said all non-essential staff had been sent home and FIFO flights would be "massively curtailed".
"We're taking extraordinary measures to ensure our workforce and the communities in which we operate are not impacted," Mr Everingham said.
"Now is not the time to think about profitability.""
Plans for using Rottnest as a quarantine zone and talks with hotels were under way, Mr McGowan said.
Army barracks could also be used for those "who can't quarantine or won't".
"I am not ruling anything out now - this thing happens so quickly," the premier said.
WA Police Commissioner Chris Dawson said people driving home may be quarantined at Eucla near the South Australian border or Kununurra near the Northern Territory border if they don't meet the deadline.
Mr Dawson urged drivers not to speed back and called for calm in the community.
The coast-to-coast Indian Pacific train will not take passengers but may move cargo.
Mr Dawson said police were patrolling businesses to ensure social distancing directives were not being ignored, but Mr McGowan said he was "very concerned" to see images on Saturday night of people not taking the new rules seriously.
Medical professionals have repeatedly called for schools to be closed, with St John of God Subiaco Hospital head of infectious diseases Astrid Arellano warning thousands of vulnerable West Australians would die "without strong action and decisive leadership".
Mr McGowan said schools and likely Crown Casino would be discussed at a national cabinet meeting later on Sunday.
"We put the rules in for Crown - we'll see how that develops," he said.
Major beaches may also be closed.