Perth and the Peel region were placed into a hard lockdown from Saturday after an infected traveller from overseas, who likely contracted the novel coronavirus during his two-week quarantine in a Perth hotel, visited several venues while unknowingly infectious.
"The short three-day lockdown has done the job it was designed to do," state Premier Mark McGowan told reporters in Perth on Monday.
"It was a circuit-breaker we needed to limit community spread and keep our community healthy."
Two million people in Perth and Peel's near 150,000 residents were ordered to stay home until 12.01am on Tuesday, except for essential work, healthcare, grocery shopping or exercise.
People can leave their homes when the lockdown ends but will have to wear masks at all times.
Home gatherings will be limited to 20 guests while restaurants and supermarkets will need to follow strict social-distancing rules.
These interim restrictions will remain until Friday night, McGowan said, when they would be reviewed.
Snap lockdowns, speedy tracking systems and border closures have helped Australia keep its Covid-19 numbers relatively low, with just over 29,600 cases and 910 deaths.
Meanwhile, McGowan remains locked in a verbal battle with the federal government over management of the states' quarantine schemes.
He wants Canberra to open air bases and Christmas Island to accommodate the travellers, adding that it's the Commonwealth's constitutional responsibility to handle the quarantine scheme.
Defence Minister Peter Dutton says the facilities are not fit for purpose and that states had previously agreed to the quarantine scheme.
Transtasman bubble
The travel arrangement between New Zealand and the state was paused last week, when community cases emerged.
New Zealand's Covid-19 Minster Chris Hipkins said on Monday that further advice from health officials would be considered before a decision on whether to resume quarantine-free travel is made.
Hipkins said he wanted to make a decision as soon as possible to give certainty to passengers booked on the next flight from Western Australia, due to leave on Tuesday night.
- Reuters, AAP and RNZ