Hundreds of coronavirus-infected people in Australia's worst-hit state have been caught flouting stay-at-home orders, authorities said Tuesday, prompting tougher fines.

The southern state of Victoria has endured a second wave of infections over recent weeks that the government has partly blamed on people breaking rules that restrict travel.

Residents of Melbourne, Australia's second biggest city and the capital of Victoria, are now enduring an overnight curfew, closure of non-essential businesses and mandatory mask-wearing as hundreds of new cases are recorded daily.

But 800 infected people -- or more than 25 percent of those doorknocked across Victoria -- were not at home when authorities conducted recent checks, which state Premier Daniel Andrews called "completely unacceptable".

Andrews said people infected people in Victoria can now be slapped with on-the-spot fines of almost Aus$5,000 ($3,558) -- up from Aus$1,652 -- if they are caught leaving home a second time.

The only exception will be to seek emergency medical care. Previously, outdoor exercise was allowed.

Police can also take serious rule-breakers to court, where fines of up to Aus$20,000 ($14,233) can be applied.

An additional 500 troops will also be deployed in Melbourne to help health officials go door-to-door checking on people who should be staying at home, Andrews said.

Victoria police commissioner Shane Patton said hundreds of officers were also on the streets to enforce the curfew, mask-wearing and stay-at-home orders. 

Patton said police had observed a small but emerging trend of so-called "sovereign citizens", who believe the laws do not apply to them and were consistently flouting the rules.

"We've seen them at checkpoints baiting police, not providing a name and address," Patton said.

"On at least four occasions in the last week, we've had to smash the windows of cars and pull people out to provide details."

Just over 160 fines were handed out in Victoria in the past 24 hours, including to a woman who was charged over allegedly smashing a police officer's head into concrete after being questioned for not wearing a mask.

Victoria has recorded more than 12,000 of almost 19,000 total coronavirus cases across Australia, as well as 147 fatalities of the country's total of 232.