The Australian flag has been soaked in fake blood and burned at a series of anti-monarchy rallies across the country.
Protesters at Melbourne's Birrarung Marr, an inner-city park by the Yarra River, cut up the flag while chanting "Abolish the monarchy".
Greens senator Lidia Thorpe led hundreds of protesters through the city on the Queen's National Day of Mourning.
"The Crown's boot is on our neck and we're sick of it," Senator Thorpe told the rally.
"Do you know we have over 20,000 Aboriginal children who have been stolen in 2022? And you want to mourn the coloniser who brought the pain and the genocide and the murders here to our people. Shame!"
The crowd then sat at the intersection of Flinders and Swanston streets, before marching to state parliament.
Senator Thorpe decried countless atrocities and human rights violations against First Nations people.
"While everyone mourns the Queen, we have 10-year-old babies trying to take their lives in Don Dale prison. We have to shut the child prisons down," she said.
In 2007, Indigenous youths accounted for 59 per cent of the total juvenile detention population. Last year, Aboriginal and Torres Strait Islander prisoners made up 30 per cent of all inmates.
The Melbourne rally was one of several protests across Australia.
In Adelaide, a man was removed from Government House after he was heard chanting anti-monarchy slogans.
Police asked the 31-year-old from Mile End to leave the area, but he refused. He was escorted from the premises and issued with a trespass notice not to re-enter the area for 24 hours.
In Brisbane, a small group of protesters demanded an end to centuries of British "tyranny".
"We don't need the numbers, we just need the passion," one protester said.
Activist groups Warriors of the Aboriginal Resistance and Fighting In Solidarity Towards Treaties were among those organising the demonstrations.
"This is a stance against the continued crimes committed against marginalised First Nations, black, brown and Asian communities," the organisers wrote on Facebook.
"This is a demonstration against racist colonial imperialism."
Another rally took place in Sydney, and a mural of the Queen in Marrickville was painted over with the black, red and yellow colours of the Aboriginal flag.
Ahead of the nationwide protests, Indigenous Australians Minister Linda Burney was asked about the monarchy and the country's history of colonisation.
"There is a huge respect, it's part of Aboriginal culture, and the reverence to the Queen in my view falls into that category," she told the ABC.
"But clearly there is a complex relationship between First Nations people and the monarchy, not so much the Queen."
Ms Burney was among hundreds of people who attended an official service in the Queen's honour at Parliament House.
"I think that's a respectful thing to do, the way we're participating today," she said.
"But you can't divorce the issues of colonisation from the role of Britain, going back through the ages."