Australia reported a record 502 new coronavirus infections Wednesday, nearly four months after the epidemic initially peaked, with authorities warning the country was entering a critical new phase.

Most of the new cases were reported in the southeastern state of Victoria, where authorities have struggled to bring an outbreak in Melbourne under control despite an almost two-week lockdown in Australia's second-biggest city.

Australia's new coronavirus infections previously peaked on March 28 when 459 cases were reported, according to data compiled by AFP. Australia had since appeared to bring the virus under control and had eased restrictions. Like neighbouring New Zealand, it had won plaudits for its pandemic response.

Victoria Premier Daniel Andrews announced 484 new cases and two more deaths in the state Wednesday, bringing its total of active cases to just over 3,400. Australia has now recorded almost 13,000 cases of the virus and 128 fatalities in a country of about 25 million.

Melbourne residents will be required to wear masks outside from midnight -- making the city the first place in Australia to mandate face coverings in public -- in a new effort to slow the virus spread. But Andrews said "further behaviour change" would still be required after analysis showed almost nine in 10 people recently diagnosed with coronavirus did not self-isolate between feeling sick and getting tested.

Just over half of the new patients also failed to stay at home while waiting for their test results, he added, saying authorities believed insecure work conditions were a key driver of the trend. Andrews said casual workers across a range of industries, who do not get sick-leave provisions, were worried about "feeding their kids, paying their bills", but could apply for a Aus$1,500 ($1,070) hardship payment if they contract the virus.

There are growing fears about the virus spreading through vulnerable populations after outbreaks at several nursing homes, while inmates at six prisons have been confined to their cells after a guard tested positive. The outbreak has left Australia rattled and dampened hopes of a speedy economic recovery.

'Most critical'

An inquiry into how the virus spread in Melbourne heard this week that many cases were likely linked to infection control breaches at hotels used to quarantine residents returning from overseas.

Victoria has effectively been sealed off from the rest of the country in an effort to contain the virus, but new cases have been detected in neighbouring New South Wales state. New South Wales Premier Gladys Berejiklian described the coming weeks as "the most critical" since the height of the last lockdown, when the state held the mantle of Australia's hardest-hit region.

Several clusters have emerged in Sydney, which health officials believe sprung up after an infected man from Melbourne visited a popular pub. "We are not out of the woods by any stretch, quite the opposite," Berejiklian told a press conference. "We remain on high alert and we have some level of anxiety as to the extent of community transmission."

Berejiklian said new restrictions would come into force Friday to tighten rules for bars, cafes, weddings and funerals, warning they could still be extended further. "A lack of compliance now has made us go down the compulsory path and we don't apologise for that," she said.

New South Wales reported 16 new cases Wednesday, with one each also detected in Queensland and South Australia states. No significant outbreaks have been detected in less-populated regions for weeks.