Renata Voracova has reportedly had her visa application cancelled by the Australian Border Force (ABF).

She is believed to have entered Australia last month after she was granted a vaccine exemption because she had recently recovered from COVID-19, ABC News reported.

"Renata Voracova decided to drop out of the tournament due to limited possibilities for training and to leave Australia," the Czech Foreign Ministry said in a statement to Reuters.

It added that it had made a diplomatic protest and that several other players were also at the Park Hotel.

Voracova, the women's world No. 80, made her grand slam debut in doubles in 2002.

The player is the second to be held, with Djokovic still in a quarantine hotel in Melbourne following a row over a COVID-19 vaccine medical exemption.

He is awaiting the outcome of an appeal against the decision by border force to cancel his entry visa and deport him - with little hope remaining of him being able to compete in the Australian Open.

On Friday Djokovic thanked his fans for their support, saying in an Instagram post: "Thank you to people around the world for your continuous support. I can feel it and it is greatly appreciated."

His father has condemned the decision, saying his son is in "prison", the tennis champion's wife has thanked fans for support - and Australian tennis player Nick Kyrgios has called on his country to "do better".

Writing on Twitter, Kyrgios said: "Look, I definitely believe in taking action, I got vaccinated because of others and for my mums health, but how we are handling Novak's situation is bad, really bad.

"This is one of our great champions but at the end of the day, he is human. Do better."

On Thursday, Djokovic's father claimed his son has been made a scapegoat and "crucified".

Srdjan Djokovic demonstrated outside the National Assembly buildings in Belgrade and told a press conference: "He met all the required conditions for the entry and participation at the tournament that he would have certainly won, since it's Novak, the best tennis player and sportsman in the world.

"Jesus was crucified and endured many things, but is still alive among us. Novak is also crucified… He will endure."

He added: "Novak and his team filed the same type of documents as those 25 other tennis players and they didn't have any problems, just Novak. They wanted to humiliate him.

"He's not in detention, he's in prison. They took all of his stuff, even his wallet. They left him with just a phone and no change of clothes, nowhere to wash his face. He's in prison, our pride is a prisoner of these idiots."

Djokovic's wife has thanked his fans for "using your voice to send love to my husband" while he remains in a quarantine hotel.

Djokovic, who has previously spoken about his opposition to vaccination and has repeatedly refused to reveal his vaccine status, announced before setting off for the Australian Open he had received "exemption permission" to enter the country.

However, the ABF refused to let him in and said he had failed to provide appropriate evidence.

Serbia's President Aleksandar Vucic has claimed Djokovic is the victim of "political persecution" and called for Australian Prime Minister Scott Morrison to move him from the "horrific hotel" where he is being held to a private house.

Djokovic's rival, Rafael Nadal, said: "I have been vaccinated twice. If you do this, you don't have any problem to play here.

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