Serbia's president has blasted Australia for the "maltreatment" of Novak Djokovic as the world number one had his visa cancelled after arriving in Melbourne.

President Aleksandar Vucic said on Instagram he spoke with Djokovic over the phone and told him that "the whole of Serbia is with him and that our authorities are undertaking all measures in order that maltreatment of the world's best tennis player ends as soon as possible".

"In line with all standards of international public law, Serbia will fight for Novak Djokovic, justice and truth."

"Otherwise, Novak is strong, as we all know him," the Serbian leader added.

Australian Prime Minister Scott Morrison replied, saying said "no one is above rules".

"Djokovic's visa has been cancelled. Rules are rules, especially when it comes to our borders. No one is above these rules," Mr Morrison said in a tweet.

Novak Djokovic

Earlier today, Mr Djokovic's father said his son was "held captive for five hours" at Melbourne airport where he had arrived to take part in this month's Australian Open where he is the nine-time champion.

"I have no idea what is going on," Srdjan Djokovic told Sputnik Serbia media outlet.

"This is a fight for a libertarian world, this is not just a fight for Novak, but a fight for the whole world."

He even threatened taking protests to the streets if his son was not released "in half an hour".

Australia border officials said the entry visa of the 34-year-old Mr Djokovic was cancelled for failing to meet strict entry requirements.

"Non-citizens who do not hold a valid visa on entry or who have had their visa cancelled will be detained and removed from Australia," the Australian Border Force said.

The Serb star landed in Melbourne after celebrating on social media that he had a medical exemption to play in the Australian Open without proof he was fully vaccinated against Covid-19.

The exemption, granted by tournament organisers after his application had been cleared by two medical panels, sparked fury among Australians who have endured lockdowns and restrictions for two years.