Locked in a dispute over his COVID-19 vaccination status, Novak Djokovic was confined to an immigration detention hotel in Australia on Thursday as the No. 1 men's tennis player in the world awaited a court ruling on whether he can compete in the Australian Open later this month.

Djokovic, a vocal skeptic of vaccines, had traveled to Australia after Victoria state authorities granted him a medical exemption to the country's strict vaccination requirements. But when he arrived late Wednesday, the Australian Border Force rejected his exemption as invalid and barred him from entering the country.

A court hearing on his bid to stave off deportation was set for Monday, a week before the season's first major tennis tournament is set to begin. The defending Australian Open champion is waiting it out in Melbourne at a secure hotel used by immigration officials to house asylum seekers and refugees.

Djokovic is hoping to overtake rivals Rafael Nadal and Roger Federer and win his 21st Grand Slam singles title, the most by any player in men's tennis.

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Djokovic's securing of an exemption so that he could play triggered an uproar and allegations of special treatment in Australia, where people spent months in lockdown and endured harsh travel restrictions at the height of the pandemic.

After his long-haul flight, the tennis star spent the night at the airport trying to convince authorities he had the necessary documentation, to no avail.

“The rule is very clear,” Australian Prime Minister Scott Morrison said. “You need to have a medical exemption. He didn’t have a valid medical exemption. We make the call at the border, and that’s where it’s enforced.”

Health Minister Greg Hunt said the athlete's visa was canceled after border officials reviewed Djokovic’s medical exemption and looked at "the integrity and the evidence behind it.”

The grounds on which he was granted an exemption were not immediately disclosed.

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While Djokovic has steadfastly refused to say whether he has gotten any shots against the coronavirus, he has spoken out against vaccines, and it is widely presumed he would not have sought an exemption if he had been vaccinated.

A federal judge will take up the case next week. A lawyer for the government agreed the nine-time Australian Open champion should not be deported before then.

“I feel terrible since yesterday that they are keeping him as a prisoner. It’s not fair. It’s not human. I hope that he will win," Djokovic's mother, Dijana, said after speaking with him briefly by telephone from Belgrade.

She added: "Terrible, terrible accommodation. It’s just some small immigration hotel, if it’s a hotel at all."

Australia’s home affairs minister, Karen Andrews, said Friday that Djokovic could fly out of the country on the first available flight.

“Can I say, firstly, that Mr. Djokovic is not being held captive in Australia. He is free to leave at any time that he chooses to do so,” Andrews said. "And Border Force will actually facilitate that.”

Serbian President Aleksandar Vucic has also spoken to Djokovic and said his government asked that the athlete be allowed to move to a house he has rented and “not to be in that infamous hotel.”

He said Djokovic has been treated differently from other players.

“I’m afraid that this overkill will continue," Vucic said. "When you can’t beat someone, then you do such things.”

Border Force investigations were continuing into two other people who arrived in Australia for the tennis tournament, Andrews said.

Australia's prime minister said the onus is on the traveler to have the proper documentation on arrival, and he rejected any suggestion that Djokovic was being singled out.

“One of the things the Border Force does is act on intelligence to direct their attention to potential arrivals,” he said. “When you get people making public statements about what they say they have, and they’re going to do, they draw significant attention to themselves.”

Anyone who does that, he said, “whether they’re a celebrity, a politician, a tennis player . . . they can expect to be asked questions more than others before you come.”

The medical-exemption applications from players, their teams and tennis officials were vetted by two independent panels of experts. An approved exemption allowed entry to the tournament.

Acceptable reasons for an exemption include major health conditions and serious reactions to a previous dose of the COVID-19 vaccine. A COVID-19 infection within the previous six months has also been widely reported to be grounds for an exemption, but that's where interpretations appeared to differ between the federal level, which controls the border, and tennis and state health officials.

Former Australian Open tournament director and Davis Cup player Paul McNamee said the treatment of Djokovic was unfair.

“The guy played by the rules, he got his visa, he arrives, he’s a nine-time champion and whether people like it or not he’s entitled to fair play,” McNamee told the Australian Broadcasting Corp. "There’s no doubt there’s some disconnect between the state and the federal government.

“I hate to think politics are involved but it feels that way.”

Djokovic tested positive for the coronavirus in June 2020 after he played in a series of exhibition matches that he organized without social distancing amid the pandemic.

Critics questioned what grounds Djokovic could have for the exemption, while supporters argued he has a right to privacy and freedom of choice.

Many Australians who have struggled to obtain COVID-19 tests or have been forced into isolation saw a double standard.

Tension has grown amid another surge of COVID-19 in the country. Victoria state recorded six deaths and nearly 22,000 new cases on Thursday, the biggest one-day jump in the caseload since the pandemic began.

Australian Open tournament director Craig Tiley has defended the “completely legitimate application and process” and insisted there was no special treatment for Djokovic.

Twenty-six people connected with the tournament applied for a medical exemption and, Tiley said, only a “handful” were granted. None of those have been publicly identified.