The 34-year-old was granted a medical exemption from COVID-19 vaccination requirements to compete in the year's first major, but after a public outcry in Australia he was detained by officials at the border on Thursday.
Djokovic is now in a quarantine hotel in Melbourne after his lawyers secured an agreement for him to stay in the country for a court hearing on Monday in which he hopes to overturn the federal government ban on his entry.
"They're keeping him in captivity. They're stomping all over Novak to stomp all over Serbia and Serbian people," Djokovic's father Srdjan told reporters at a news conference in Belgrade on Thursday.
Australian Prime Minister Scott Morrison said earlier in the day that Djokovic would receive no special treatment.
"Morrison and his like have dared attack Novak to bring Serbia to its knees. Novak has always shown that he comes from a proud nation," Srdjan said.
"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," he added.
Earlier in the day, Srdjan described his son to the Telegraf website as "the Spartacus of the new world that doesn't tolerate injustice, colonialism and hypocrisy."
Djokovic's mother Dijana, who also attended the conference alongside the player's brother Djordje, described the situation as "scandalous".
"They want to clip his wings, but we know how strong he is," she said.
Djokovic's family displayed his nine Australian Open trophies at the conference, adding that they would organise a support rally in front of Serbia's parliament building in the city centre.
Former mentor Niki Pilic, who oversaw Djokovic's career as a teenager, told Reuters that the situation was "farcical", adding: "Politics have interfered with sports here as it so often does."
Pilic said Morrison was "trying to please a part of the country's society and improve his poor political rating."
Former Yugoslavia Davis Cup coach Radmilo Armenulic said Djokovic had been treated "like a felon".
"They detained him under police presence. He was held in a room for eight hours after he was cleared to take part in the Australian Open by the medical panel," Armenulic said.
"This decision, in my opinion, reflects lawlessness and not the rule of law. They have treated Novak like a criminal and a villain to stop him from winning his 21st grand slam."
