Police in Melbourne used pepper balls and rubber pellets to scatter thousands of protesters who defied stay-at- home orders to damage property, block a freeway and injure three officers, leading to over 40 arrests.
It was the second day of demonstrations in the locked-down Australian city after authorities shut construction sites for two weeks, saying workers' frequent movement was spreading the coronavirus.
"This has been a really challenging environment for us," Shane Patton, police commissioner in the southeastern state of Victoria, told reporters, adding that the protests were unlawful.
Television and social media showed video images of protesters marching through the streets, sending up flares, chanting and attacking police cars, surrounded by mounted police and officers in riot gear.
The protesters included not only construction workers but opponents of mandatory vaccinations and Victoria's extended lockdown, who cursed the jab, state premier Dan Andrews and the workers' union leader, who had backed vaccination for members.
"Acts of violence and disruption won't result in one less case of COVID - in fact it only helps the virus to spread," Andrews, the state premier, said in a statement late on Tuesday.
The halt in building activities followed a protest against a vaccine mandate that turned violent on Monday. The state requires all construction workers to receive at least one vaccine dose by the end of this week.
"The public health team was left with no choice but to hit the pause button and continue to work with the sector over the next two weeks to improve compliance," state Health Minister Martin Foley told reporters.
The forced closures of building sites will worsen Australia's economic woes, with some economists forecasting the extended lockdowns could push the A$2 trillion ($1.45 trillion) economy into a second recession in as many years.
Australia has locked down its largest cities of Sydney and Melbourne, as well as the capital, Canberra, to rein in an outbreak of the highly infectious Delta variant.
But the tough curbs have triggered anti-lockdown rallies with police arresting hundreds in both cities over the weekend.
Tuesday's 603 new infections in Victoria were the highest daily figure this year, with one new death was recorded.
Authorities have begun to ease some strictures on outdoor gatherings and exercise in Sydney and Melbourne as vaccination rates rise, with more freedom promised once 70 per cent to 80 per cent of adults in the population have received both vaccine doses.
Until now, 53 per cent have been fully vaccinated in the state of New South Wales, home to Sydney, while in Victoria the coverage is 44 per cent.
Even with the Delta outbreaks, Australia's COVID-19 infections are lower than many comparable nations, with 88,700 cases and 1,178 deaths.