COVID-19: Australia's Victoria announces 725 coronavirus cases, 15 deaths in the fourth day of strict lockdown

The Australian state of Victoria has reported 725 new cases of coronavirus and 15 deaths.

It is the highest daily number of cases in a single day for Australia since the pandemic began in January, after reporting its second-highest increase of 723 new infections on Thursday.

In the past 24 hours, a man in his 30s, three men and a woman in their 70s, three men and three women in their 80s, and three men and a woman in their 90s died.

"Of those 15 cases, 12 can be linked to aged care," Premier Daniel Andrews said.

Currently, 538 Victorians are in hospital with 42 in intensive care, he said.

Andrews added there are now 7227 active cases in the state - 1435 of which are linked to aged care facilities.

Victoria's largest city, Melbourne, entered a state of disaster and a strict lockdown on Sunday as the state's COVID-19 crisis showed little signs of letting up. It's expected to be in place for at least six weeks.

"We are all in this together and the decisions that we all make as individuals, as families [and] as communities - they have an impact  on all of us," Andrews said.

"If we all continue to do as we should - making better choices - then we'll keep our communities safe and we will get to the other side of this. The alternative, of course, is these restrictions lasting for much longer than they should - no-one wants that."

The state reported 439 cases on Tuesday and has now recorded over 13,000 infections.