The snap lockdown in Victoria will be in place for at least seven days after the state recorded seven new COVID-19 cases.
Residents now have just five reasons to leave their homes include purchasing foods and supplies, exercising for up to two hours, giving care, essential work and education or getting a COVID-19 test or vaccination.
Shopping and exercise must be done within 5km of households.
Face masks will remain mandatory at all indoor and outdoor areas that are not homes.
There are now an estimated 10,000 people in isolation after contact tracers identified at least 80 exposure sites.
They include a meat processing site and a Virgin Australia flight from Sydney to Melbourne on August 2.
Just three of yesterday's cases were linked to a known outbreak.
It's feared a mystery case from Sydney may have sparked Victoria's latest coronavirus infection, having an illegal visitor when they were meant to be isolating.
A pop-up testing clinic will be offering Pfizer vaccines in what's believed to be a first for Victoria. That will be located at the Al-Taqwa College in Truganina, where a teacher worked while infectious with the virus.
Overnight, police made 15 arrests following a late-night anti-lockdown protest through Melbourne.
Video of the rally showed people, many of them maskless, walking through the city last night and chanting "Free Victoria", "sack Dan Andrews" and "no more lockdown".
Another video appeared to show police using pepper spray to deter some protesters, who began to gather about 7pm.