Western Australia will impose tougher restrictions on people returning or travelling from Victoria and has detected one new COVID-19 case in a woman who flew to Perth without permission.
However, no new cases have been linked to a coronavirus-positive NSW truck driver who visited WA and South Australia last week.
With Victoria posting 733 new infections on Friday and the state's two-week rolling average now above 500, WA has declared it a region of extreme risk.
That means no one will be allowed to travel from Victoria unless there are extraordinary circumstances, with the hard border to come into force from Wednesday next week.
Premier Mark McGowan said it was "heartbreaking" to see what was happening in Victoria and NSW while at the same time urging anyone who wanted to come home to do so in the next few days.
"Our thoughts are with our fellow Australians, but we have to act now," he said.
"Growing case numbers are simply too big a threat."
The premier said the new infection, detected in the woman who flew into Perth from NSW on Tuesday, was not considered a risk to the wider community.
He said she was thought to be a returning Western Australian but was directed into hotel quarantine.
The woman subsequently tested positive for the virus and would now spend 14 days in isolation in Perth.
Fifteen people who travelled on the same flight have also been placed in quarantine and have so far tested negative.
The new case came just a day out from the AFL grand final in Perth but was not expected to impact the game.
Mr McGowan said the final would be a historic event for the state and he was "confident we will do the big match justice".
"We will be the centre of attention across the entire country," he said.
In relation to the NSW truck driver, 47 contacts have now been identified in WA with 13 of them considered closed contacts.
Ten of those have since tested negative with three tests still pending.
Of the 34 casual contacts, 21 have tested negative so far.
Most contacts were believed to be linked to roadhouses and fuel stops where the truckie and his fellow driver stopped.
They were in WA for less than 48 hours between September 16 and 17 and travelled through South Australia on September 15 and 18.
SA authorities said no new virus cases were reported on Friday from more than 6000 tests conducted over the past 24 hours.
They have identified more than 130 contacts across about 10 exposure sites who have all been placed in isolation, either for 14 days or until they return a negative test.
The infected man, in his 20s, returned a negative test before leaving for WA, but tested positive on his return to NSW.
He has received one dose of a COVID-19 vaccine, while his colleague has so far tested negative.
Australian Associated Press