Tennis world number one Novak Djokovic has begun a third day in Australian immigration detention, joined by Czech women's player Renata Voracova as a blame game between Australian authorities over handling of Covid-19 vaccine exemptions gathered steam.

The Serbian superstar, a vocal opponent of vaccine mandates who came to Australia in hopes of winning his 21st Grand Slam at the Australian Open, has been holed up since Thursday in a modest Melbourne hotel since having his visa cancelled due to problems with a medical exemption, Reuters reported.

His lawyers are preparing a legal challenge to his visa cancellation, which is scheduled to go to a federal court hearing on Monday, and have been given until Saturday evening, local time, to file a summary of their case.