Tennis world No. 1 Novak Djokovic was joined in Australian immigration detention by Czech women's player Renata Voracova on Friday as he sought to fend off deportation over the country's COVID-19 rules and compete in the Australian Open, where he is seeking to win his record-breaking 21st Grand Slam singles title.

Both players were being kept at the modest Park Hotel in inner-city Melbourne, where scores of asylum seekers are also housed behind grey walls and locked windows.

The Czech Foreign Ministry said in a statement that 81st-ranked Voracova planned to leave after being faced with similar circumstances as Djokovic.

"Renata Voracova decided to drop out of the tournament due to limited possibilities for training and to leave Australia," it said, adding that it had made a diplomatic protest and that several other players were caught in the same situation.

Djokovic was held at the airport on Wednesday. Authorities revoked a visa granted on the basis of a medical exemption from Australia's strict vaccination requirements.

Djokovic's lawyers won legal approval for him to remain until a full court hearing against the federal government on Monday.

The Australian Border Force (ABF) said on Friday that one person had voluntarily left Australia while a third person's visa had also been canceled. It did not give names.

The family of Novak Djokovic and the president of his home country say Australia's treatment of the tennis star is part of a political agenda.

"This has nothing to do with sports, this is a political agenda. Novak is the best player and the best athlete in the world, but several hundred million people from the West can't stomach that," Djokovic's father, Srdjan, told reporters in Belgrade on Thursday.