People enjoy a mid-winter walk on Brighton Beach in Melbourne on June 22, 2021, when the city's previous Covid-19 outbreak receded. Photo: AFP / William West

Australia’s bid to quash a fast-spreading coronavirus outbreak will see the country’s second city of Melbourne return to a “hard and fast” lockdown late Thursday.

State Premier Dan Andrews said the city – and surrounding Victoria state – will join Sydney in locking down, bringing the total number of Australians under stay-at-home orders to about 12 million.

The largely Covid-free country is trying to halt an outbreak of the Delta variant, which has grown to almost 1,000 cases nationwide in a month.

Andrews said he took the decision to return Melbourne to its fifth lockdown “with a heavy heart” but it was an “absolute necessity.”

“Nothing about this virus is fair,” he said, describing how only 18 cases in Victoria had spurred thousands of contacts who must now be traced and tested.

“You only get one chance to go hard and go fast,” he said.

“If you wait, if you hesitate, if you doubt, then you will always be looking back wishing you had done more earlier.”

The lockdown will start shortly before midnight local time on Thursday and last five days.

Australia’s largest city, Sydney, is now in its fourth week of lockdown after the virus spread from overseas aircraft workers to their local driver in mid-June.

Sydney authorities said Thursday that the situation there had “stabilized” – with 65 new cases reported in the last 24 hours.

But the lockdown is set to continue for two more weeks to try and eliminate any community transmission.

Australia had been widely lauded for its early handling of the pandemic and successful “Covid zero” strategy.

But a painfully slow vaccine rollout has left only 10% of the population protected as much of the rest of the world gingerly reopens.

The lockdown rules are less stringent than some other cities have seen.

Sydney residents are allowed to leave home for exercise, essential shopping, work or health reasons, but schools are closed and people are encouraged to remain at home.

Since March 2020, Australia’s borders have been largely closed to all non-essential travel in or out.

From this month, the number of people allowed to enter the country was cut to 3,000 a week.

Before restrictions were introduced, about 250,000 visitors arrived every week.