Sweeping new coronavirus restrictions were imposed across Melbourne and other parts of Victoria from Sunday night, after a disaster was declared in the virus-hit Australian state.
Lockdown measures have been tightened and a curfew imposed in Melbourne from 8pm to 5am, the state's Premier Daniel Andrews announced.
State authorities have said the state of disaster proclamation gave police greater power.
Melbourne residents will only be allowed to shop and exercise within five km (three miles) of their homes.
People waited in long lines outside grocery stores ahead of the lockdown on Sunday, wearing masks.
Authorities said there would be more announcements about workplaces on Monday, including the closure of certain industries.
All students across the state will return to home-based learning and child care centers will be closed.
Daniel Andrews, Victoria state Premier, said: "As heartbreaking as it is to close down places of employment, and whilst I never thought that I would be telling people not to go to work, that is what we have to do in order to stop the spread of this wildly infectious virus, this deadly virus."
He added: "This six-week period is absolutely critical. We have got to make decisions, very difficult decisions but we've got to err on the side of doing everything we possibly can to drive these case numbers down."
Brett Sutton, Victoria Chief Health Officer said with the introduction of the strict measures, she expects "absolutely that we will see transmission driven down and cases to decrease over time."
He said: "These restrictions are very substantial, and I expect, absolutely expect that we will see transmission driven down and cases to decrease over time. We don't see it in the numbers instantaneously."
Mr Sutton added: "We will see the effect of universal mask wearing in the numbers in the week ahead, and ongoing. We will see the effect of these restrictions in the following week."
He continued: "But they will be ongoing and they will continue right through the six-week period where we will see a reduction in numbers week on week, as long as people are following the directions that have been laid out."