A three-week lockdown in Sydney could be extended, with the city logging its biggest rise in local COVID-19 cases for this year.
New South Wales Premier, Gladys Berejiklian pleaded with Sydney's five million residents to stay home: "New South Wales is facing the biggest challenge we have faced since the pandemic started and I don't say that lightly."
Hundreds of extra police patrolled parts of Sydney to enforce the city's lockdown.
Forty-four locally acquired cases were reported on Friday in NSW, Australia's most populous state, taking the total to more than 400 cases in the latest outbreak of the highly infectious Delta variant.
Berejiklian also rejected reports the government was considering a shift of policy to "living with the virus," citing low vaccine coverage in Australia.
Meanwhile, some good news for citizens overseas, the state of South Australia will run a trial of home quarantine, after criticism of the two-week hotel quarantine.
Hotel quarantine virus leaks have been the source of Australia's community outbreaks.
Although Australia has kept its COVID-19 numbers relatively low, its vaccination rollout has been among the slowest due to supply constraints and changing medical advice.
Roughly a quarter of hospitalisations in the Sydney outbreak are people aged 35 and under, an age bracket not yet eligible for vaccinations under the government's program.