A person who attended a mass rally in Melbourne on the weekend has been diagnosed with Covid-19.
Victoria's Chief Health Officer says the individual was unlikely to have caught the illness there as he first developed symptoms the day after.
Thousands of people may need testing.
The protest was one of several Black Lives Matter events staged around the country - including in Hobart and Launceston - in defiance of Covid-19 regulations.
The news comes after more than 2000 people expressed interest in attending an anti-racism rally in Sydney tomorrow.
Tasmanian Senator Jacqui Lambie, who asserts Aboriginal ancestry, has told Nine another protest would be wrong at this time.
"We've been in lockdown, the last thing we want to be doing is go back into lockdown," she said.
"The economy is really struggling, jobs are going to be hard to get; to put lives at risk through recklessness again, what is bloody wrong with you people? It's so un-Australian."