Authorities in the Australian city of Melbourne have warned of a "dangerous" rise in people resisting lockdown measures, sometimes violently.
Police said this trend included so-called "sovereign citizens" - who espouse an anti-government ideology - confronting officers.
In one case a woman repeatedly smashed a policewoman's head into the ground.
Authorities have increased fines for repeated rule breaches as Melbourne endures a deadly virus second wave.
More than half of Australia's 18,300 cases have been recorded in the past month in Victoria, of which Melbourne is the capital. There have been 226 deaths nationally.
Melbourne has recently mandated wearing masks and tightened a stay-at-home order to reduce transmissions.
But authorities said many people were breaking rules, including some who claimed to be "above the law".
Chief Commissioner Shane Patton said Victoria Police had seen an "emergence" of "concerning groups of people who classify themselves as 'sovereign citizens'".
The sovereign citizen movement - which has roots in the US - is typically used by those who don't believe in their government's legitimacy, often arguing their rights are being suppressed by public orders.
Mr Patton said the attack on the policewoman "highlights the type of challenges that we're experiencing", adding that people were "baiting" police at checkpoints and refusing to disclose basic information.
"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," he said.
What rules are people breaking?
"Most Victorians are doing the right thing, no question," said Victoria's Premier Daniel Andrews.
"But we have this continual minority of people who are knowingly - not by mistake, but are knowingly - doing the wrong thing and putting people's lives at risk by doing so."
Random checks by police on 3,000 infected people had found more than 800 were not home isolating, as they were supposed to be.
On Tuesday, the state government increased fines for repeated lockdown breaches from A$1,652 (£900; $1,200) to A$5,000.
Under the current "stage four" lockdown, Melburnians can leave home only to shop, exercise, give essential medical care or do frontline work.
Residents must shop and exercise within 5km (3 miles) of their home, for no longer than one hour at a time.
An additional curfew for between 20:00 and 05:00 was implemented on Sunday. The only exemptions are for work, medical care or care-giving, and workers must have a permit.
Authorities said recent breaches included "Airbnb parties" and people breaking the curfew to get alcohol and fast food.
Mr Patton said the policewoman had been attacked in a shopping centre after stopping a woman for not wearing a mask.
"After a confrontation and being assaulted by that woman, those police officers went to ground and there was a scuffle," he said.
"And during that scuffle, this 38-year-old woman smashed the head of the policewoman several times into a concrete area on the ground."
Since masks became compulsory about two weeks ago, there have been other prominent incidents involving "anti-maskers" and others questioning the legality of lockdown.
Widely shared videos include two women loudly defending not wearing a mask inside a hardware shop, and one woman deceiving police at a state border checkpoint.
Australia had much early success in tackling Covid-19, but the outbreak in Victoria's state capital has pushed the nation to its worst position yet.