"I can’t rule out we have further limits placed on people’s movement. I can’t rule that out," he told reporters.
"If you don’t want a stage four, if you don’t want the lockdown to last a moment longer, then please follow the rules. Do the right thing by your family, your community, and every family."
It comes as metropolitan Melbourne is seeing unprecedented levels of community transmission.
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So, what exactly would a stage four lockdown entail?
Since the pandemic began, no Australian state or territory has entered a stage four lockdown - meaning there is no government guide outlining what further measures may include.
New Zealand was in stage four lockdown from March 25, and remained there for 10 weeks. The country achieved substantial success in slowing the spread of COVID-19 under their stage four lockdown, temporarily eliminating the virus from their shores (until overseas travellers returned and re-introduced it).
The Prime Minister has announced New Zealand Covid-19 Alert Levels. Here is a table that explains what they mean. This information will be available on the https://t.co/vEvj37KKdO website shortly. pic.twitter.com/1iW7L75AfY— National Emergency Management Agency (@NZcivildefence) March 20, 2020