The tennis star has been placed under guard ahead of a federal court hearing regarding his possible deportation.
Australia has detained Novak Djokovic for a second time, calling the tennis star a threat to public order while fighting in court to deport him.
Djokovic was placed under guard on Saturday at an undisclosed Melbourne location believed to be his lawyers' offices. A federal court hearing is scheduled for Sunday.
He is expected to spend Saturday night in immigration detention, after a few short- lived days of freedom following his first successful court appeal.
Djokovic's presence in Australia "may foster anti-vaccination sentiment", immigration minister Alex Hawke argued, justifying his use of broad executive powers to revoke the ace's visa.
Not only could Djokovic encourage people to flout health rules, Hawke said, but his presence could lead to "civil unrest".
With just two days before the Australian Open begins, the defending champion is again focused on law courts rather than centre court.
This is the second attempt by Australia's conservative government to deport Djokovic, one of the world's most high-profile Covid-19 vaccine sceptics.
After months of speculation about whether Djokovic would get vaccinated to play in Australia, he used a medical exemption to enter the country a week ago, hoping to challenge for a record 21st Grand Slam title at the Open.
Many Australians, who have suffered prolonged lockdowns and border restrictions, believe Djokovic gamed the system to dodge vaccine entry requirements.
Amid public outcry, Prime Minister Scott Morrison's government revoked Djokovic's visa on arrival.
But a judge reinstated Djokovic's visa and allowed him to remain in the country.
This time, the government has invoked exceptional and difficult to challenge executive powers to declare him a threat to public health and safety.