Victoria Premier Daniel Andrews has announced the state recorded 428 new cases of COVID-19 and three additional deaths on Friday.
It's Australia's largest daily increase yet and follows the state reporting 317 cases on Thursday.
Friday's alarming spike brings Victoria's total number of cases to 5165. There are 122 people in hospital and 31 in intensive care.
The people who died were a man and woman in their 80s, and a man in his 70s, Andrews told a news briefing on Friday. It brings the state's death toll 32.
Andrews said 24,409 tests were completed in the past 24 hours.
Melbourne and surrounding Mitchell Shire were put into a six-week lockdown last week. People are only allowed to leave the house for work, school and essentials during this lockdown.
"That ring around Melbourne and Mitchell Shire is working in terms of reducing the spread of this virus into regional Victoria but it can change," Andrews told reporters. "It can change if people don't follow the rules, it can change if people have symptoms and go about their business as if they didn't.
"It can certainly change if people pretend this is over because they really want it to be."
Neighbouring New South Wales, meanwhile, recorded eight new COVID-19 cases overnight - six of which were community transmitted, Premier Gladys Berejiklian said.