Sydney residents were warned Monday to put the brakes on partying as a new coronavirus cluster emerged at a city pub on the heels of a major outbreak in Melbourne.

Three pubs in Sydney and its surrounds were closed after being linked to outbreaks or failing to comply with social distancing requirements, while other events were under investigation with Australia on edge over a resurgence of the virus.

The new cluster emerged after Melbourne entered a six-week lockdown on Thursday, and surrounding Victoria state was sealed off from the rest of the country in an effort to contain the virus.

Authorities reported 177 new infections in and around Melbourne Monday, marking a week of triple-digit increases.

New South Wales police assistant commissioner Tony Cooke on Monday slammed the "moronic behaviour of people at dance parties", after local media published footage of large private get-togethers in Sydney's wealthy eastern suburbs.

City residents are allowed a maximum of 20 visitors to their homes under restrictions which have been gradually eased in recent weeks as the number of infections dwindled.

At least 21 infections have now been linked to a growing cluster at Sydney's Crossroads Hotel -- a popular drinking spot on a major traffic route -- raising concern the virus could be spreading in the state.

Police patrol near the Sydney Opera House, an area usually thronged with tourists, during Australia's coronavirus outbreak
Police patrol near the Sydney Opera House, an area usually thronged with tourists, during Australia's coronavirus outbreak AFP / Saeed KHAN

A dozen military personnel who visited the pub while poised to deploy on an anti-virus mission were on Monday in isolation at an army base in rural New South Wales.

The state's police minister David Elliott warned that if the situation was not brought under control, pubs could be closed again.

"If we have to close hotels and clubs again, the patrons will have to take some of the ownership of that," he told a press conference Monday.

"I will, however, work to my dying breath to make sure that that doesn't happen."

Police have stepped up penalties for breaching coronavirus restrictions in recent days, with almost Aus$220,000 ($153,000) in fines handed out across Melbourne in the past 24 hours.

On Friday, a group whose house party was exposed by their large KFC order was fined Aus$26,000 while six people from Victoria who tried to cross Queensland's border illegally were each fined Aus$4,000 the following night.

Australia has recorded just under 10,000 coronavirus cases and 108 fatalities.

Most states and regions have reported few or no new daily cases of the disease in recent weeks, allowing much of the country to ease restrictions on movement and gatherings.