Coronavirus lockdowns are likely to be lifted in two major Australian cities this week, authorities said Monday, as outbreaks of the Delta variant were brought under control.

Around half of Australia's 25 million largely unvaccinated residents are currently under stay-at-home orders.

But while the largest city Sydney struggled to bring its outbreak to heel, the states of Victoria and South Australia reported progress.

South Australia premier Steven Marshall said Monday that a week of stay-at-home orders would "most likely be lifted" in the early hours of Wednesday.

The state, which includes the city of Adelaide, reported one new infection on Monday, a case already in isolation.

Some restrictions will remain in place.

"We won't be going directly back to where we were," said Marshall, outlining lingering rules on social distancing and mask-wearing.

Restaurants will be seated-only and a ban on shisha pipes, dancing and singing will remain.

Similarly, authorities in Victoria -- which includes Australia's second city Melbourne -- said the state was "on the right track" to also lift its lockdown early Wednesday.

The coronavirus lockdown in Melbourne is likely to be lifted this week as an outbreak was brought under control
The coronavirus lockdown in Melbourne is likely to be lifted this week as an outbreak was brought under control AFP / Con Chronis

Victoria reported 11 new cases on Sunday, but all were in quarantine.

But the state's Health Minister Martin Foley cautioned that a final decision had yet to be made and the situation has been fast-changing.

Melbourne began its fifth lockdown earlier this month.

In Sydney, the picture was less rosy.

The city is struggling with its most serious Covid-19 outbreak to date, recording 145 new cases Monday as the outbreak grew to 2,226 cases.

Sydney's month-long lockdown is almost certain to be extended on Friday.

Last week, the New South Wales state premier suggested restrictions could remain in place for another month or more, fuelling a thousands-strong protest on Saturday that was widely condemned.

Since the pandemic began, Australia has recorded about 33,000 infections and 918 Covid-related deaths.

Just 13 percent of Australians have been vaccinated, with poor supplies of Pfizer-BioNTech shots and scepticism about the AstraZeneca jab.