Victoria has recorded 317 new cases of COVID-19, bringing the total number of cases to 4750.
Victorian Premier Daniel Andrews said two men in their 80s had died overnight.
Mr Andrews said it was "so, so important" the lockdown rules were followed.
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NSW recorded 10 new cases in the last 24 hours, but more have been found in the hours since.
Locally, Murrumbidgee Local Health District have confirmed no new cases of COVID-19 have been detected on the border.
Health authorities are gravely concerned about coronavirus outbreaks in nursing homes, while several staff at a children's hospital have also been infected.
Deputy Chief Medical Officer Michael Kidd is watching Victorian case numbers rise each day.
Professor Kidd is also keeping a close eye on the number of people admitted to hospital, particularly those in intensive care.
"And of course we are gravely concerned about the number of residential aged care facilities where we have seen cases of COVID-19," he told the ABC on Thursday.
Eight Victorian aged care facilities have residents with coronavirus, while a further 24 nursing homes have staff infected.
Experts are also investigating how a handful of staff at the Royal Children's Hospital in Melbourne contracted coronavirus.
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"I don't know whether the source of infection has been out in the community or related to the hospital," Professor Kidd said.
Victorians are bracing for harsher lockdowns after the state recorded yet another day of triple-figure infections.
Victoria's chief health officer Brett Sutton has not ruled out a move to stage four restrictions which could see more businesses forced to close and further limits on travel.
Federal Health Minister Greg Hunt says avoiding such restrictions should be the fundamental goal in Victoria and the rest of the country.
"All of these people are doing it tough as it is already," Mr Hunt said.
"Higher levels of lockdown would mean even greater hardship for individuals, mental health, social isolation, the elderly who'll be isolated."
In NSW, there are now 34 cases linked to a pub in southwestern Sydney, prompting tighter restrictions at licensed venues.
NSW Health confirmed the "patient zero" of the cluster linked to the Crossroads Hotel was a Melbourne freight company employee who attended the Casula pub for a work party on July 3.
Professor Kidd is waiting to see how large the coronavirus cluster becomes.
The Northern Territory has declared the entire area of greater Sydney a hotspot in relation to travel restrictions, while Queensland has singled out Campbelltown and Liverpool.
Returned overseas travellers have left Western Australia with its biggest active caseload in five weeks, with all 29 people in hotel quarantine.
- with Australian Associated Press