World number one tennis player Novak Djokovic was denied entry into Australia on Thursday amid a storm of protest about a decision to grant him a medical exemption from COVID-19 vaccination requirements to play in the Australian Open.

The tennis star was transported to a quarantine hotel in Melbourne after being held at the city's airport overnight and was told he would be removed from the country later on Thursday, a source close to the tournament told Reuters.

The saga, fuelled by domestic political point-scoring about the country's handling of a record surge in new COVID-19 infections, created an international incident with the Serbian president claiming harassment of its star player.

Australia's Border Force confirmed Djokovic's visa had been revoked, while the source said the player's lawyers planned to file an injunction to prevent his removal.

"There are no special cases, rules are rules," Australian Prime Minister Scott Morrison said at a televised media briefing.

"We will continue to make the right decisions when it comes to securing Australian borders in relation to this pandemic," Morrison said.

Djokovic, who has consistently refused to disclose his vaccination status while publicly criticising mandatory vaccines, kicked off the furore when he said on Instagram that he had received a medical exemption to pursue a record-breaking 21st Grand Slam win at the Open starting January 17.

The announcement prompted outcry in Australia, particularly in tournament host city of Melbourne, which has endured the world's longest cumulative lockdown to ward off the coronavirus.

Australia's adult vaccination rate of about 91% is high by international standards and there is little public sympathy for those who refuse to be inoculated, as the Omicron variant sends case numbers to record levels.

However, the move by the Australian government to block his entry caused ructions between Canberra and Belgrade.

Serbian President Aleksandar Vucic said he had spoken with Djokovic to reassure the player "that the whole of Serbia is with him and that our bodies are doing everything to see that the harassment of the world's best tennis player is brought to an end immediately."

"In line with all norms of international law, Serbia will fight for Novak, truth and justice," Vucic said on Twitter.

Morrison said he was aware that "representations have been made" by the Serbian embassy in Canberra and denied the claims of harassment.

"Australia has sovereign borders and clear rules that are non-discriminatory," Morrison said.

Serbian media reported that Vucic had summoned the Australian ambassador in Belgrade and demanded Djokovic be released and allowed to play.

In a dramatic series of events, Djokovic's father told media in Serbia that his son was ushered into an isolation room under police guard when he touched down at Melbourne's Tullamarine airport at about 11:30 p.m. (1230 GMT) on Wednesday after a 14-hour flight from Dubai.

His fate was the focus of a political bunfight in Australia, characterised by fingerpointing between Morrison's conservative administration and the left-leaning Victorian government led by Premier Dan Andrews.

Under Australia's federal system, states and territories can issue exemptions from vaccination requirements to enter their jurisdictions. However, the federal government controls international borders and can challenge any exemptions granted by states.

Djokovic travelled to Australia after receiving an exemption from the Victorian government, granted after a process that included a panel of health officials. That exemption - the reasons for which are not known - supported his federal government-issued visa to play at the Australian Open.

On arrival, however, Federal Border Force officials at the airport said Djokovic was unable to justify the grounds for his exemption.

The Australian task force that sets the exemption parameters lists the risk of serious cardiac illness from inoculation and a COVID-19 infection within the past six months as qualifiers. However, Morrison said on Thursday that Tennis Australia had been advised several months ago that a recent infection did not meet the criteria for exemption.

The squabbling overshadowed the fact that Australia's daily COVID-19 infections hit a record high for the fourth consecutive day, with new cases exceeding 72,000, overwhelming hospitals and causing labour shortages.

Tennis Australia and government officials said Djokovic received no preferential treatment, adding he was among "a handful" of the 26 people who applied who were approved in an anonymous and independent process.

With just 11 days to go until the Open starts, a legal challenge could go all the way to the High Court.

Angry Aussies

The Serbian has won nine titles at Melbourne Park including the last three, but his anti-vaccination stance means he faces a tough crowd to take his tenth in Victoria.

Australian tennis great Rod Laver, after whom the main showcourt is named, warned that Djokovic would likely face hostility.

"I think it might get ugly," Laver told News Corp. "I'd think the Victorian people would be thinking 'Yes I'd love to see him play and compete, but at the same time there's a right way and a wrong way'.

Paul McNamee, former Australian Open tournament director and tennis professional, said Djokovic had followed the required steps to obtain a visa and should be allowed to play.

"So he deserves his day on court, not in court, in my opinion," McNamee told ABC TV.