Djokovic faces deportation after his visa application was cancelled - having thought he could enter Australia through a medical exemption to avoid COVID vaccination.

A court hearing today was expected to return a decision on his fate, but a judge adjourned proceedings until 10am on Monday local time.

The 34-year-old Serbian player appealed the decision to deny him entry after being held up for several hours at Melbourne Airport.

The world number one will stay in immigration detention until the hearing.

Evidence for medical exemption 'found to be insufficient'

Australia's Prime Minister, Scott Morrison, said Djokovic had failed to provide sufficient proof to receive a medical exemption to COVID-19 vaccination rules.

"All I can say is that the evidence (for) medical exemption that was provided was found to be insufficient," Mr Morrison said.

He added that Djokovic had not been "singled out" for scrutiny.

Djokovic was under armed guard and alone in a room at Melbourne Airport as he waited to hear whether he would be allowed into the country, his father said.

The star, who has repeatedly refused to say whether he has received a coronavirus vaccine, said on Tuesday he had been granted an exemption to allow him to compete in the Australian Open.

'In some ways I feel sorry for him'

Rafael Nadal, who is tied with Djokovic and Roger Federer with 20 Grand Slam singles titles, said: "I think if he (Djokovic) wanted, he would be playing here in Australia without a problem.

"He makes his own decisions, and everybody is free to take their own decisions, but then there are some consequences.

"Of course I don't like the situation that is happening. In some way I feel sorry for him but at the same time, he knew the conditions since a lot of months ago, so he makes his own decision."

Daniil Medvedev, who is ranked No. 2 behind Djokovic on the men's tour, said: "If he had a fair exemption from the rule, well, he should be here; if he didn't, he shouldn't be here."

Serbia's president criticises 'harassment'

Serbia's president, Aleksandar Vucic, criticised the "political persecution" of Djokovic.

Mr Vucic said: "What's not fair is this political persecution, that everyone is taking part in, even the Australian prime minister."

He said Serbia's prime minister, Ana Brnabic, was "asking just one thing: to let Novak Djokovic move out from this horrific hotel into a rented home where he can prepare for the tournament, while he is awaiting a court decision on Monday."

He added: "In this house, he can be under surveillance 24 hours."

Two-time quarterfinalist Tennys Sandgren, who is not playing the Australian Open this year because of the vaccination requirement, tweeted: "Just to be crystal clear here. 2 separate medical boards approved his exemption. And politicians are stopping it. Australia doesn't deserve to host a grand slam."

Paul McNamee, who was director of the Australian Open for 12 years, said: "He played by the rules, he got his exemption, he's a nine-time champion, whether people like it or not he's entitled to fair play. He doesn't make the rules. He deserves his day on court, not in court in my opinion."

Star refuses to reveal vaccination status

Djokovic has refused to say whether he has received a COVID vaccine.

He previously tested positive after hosting a controversial tennis tournament across eastern Europe.

In April 2020, he revealed he was an anti-vaxxer and said a mandated vaccination programme could get in the way of his return to competitive tennis.

Australia suffers record COVID cases

It comes as Australia is currently suffering record COVID cases fuelled by the Omicron strain of the virus.

With Thursday's count still incomplete, Australia so far has reported 72,392 new infections easily exceeding the high of 64,774 set a day earlier. Western Australia is due to post its new cases later.

Having successfully kept a lid on its COVID-19 caseload through aggressive lockdowns earlier in the pandemic, Australia is now suffering infections rates far higher than elsewhere in the Asia-Pacific region, and some epidemiologists in the country predict that the worst is yet to come.