Anger towards Australian swimmer Mack Horton has again boiled over on Chinese social media, with millions of people directing their fury at the Rio gold medallist over his refusal to share a podium after being beaten by Sun.

Key points: Chinese social media users have violated their own country's internet censorship rules to attack Mack Horton

Chinese social media users have violated their own country's internet censorship rules to attack Mack Horton Chinese media has avoided editorials about the rivalry between Horton and Chinese star Sun Yang

Chinese media has avoided editorials about the rivalry between Horton and Chinese star Sun Yang Another flare-up between Mack Horton and Sun has been avoided, with Horton failing to qualify to face Sun in the 800m final

The rivalry between the pair again flared this week when Sun's celebration for his 400 metre freestyle win at the world championships in South Korea was overshadowed by Horton refusing to shake his hand and stand next to him on the podium.

Horton has long been critical of swimming authorities for allowing the Chinese star to compete after serving a three-month suspension in 2014 for testing positive to a banned stimulant, and last year smashing a blood vial during a dispute over the process of a random drug test.

Horton's actions were bound to spark anger in China, where nationalism is heavily fanned by the ruling Communist Party, and over the past 48 hours his social media accounts have been bombarded by Chinese users violating their own country's internet censorship rules by jumping over the great firewall to abuse him.

On China's main public social media platform Weibo, a post about Horton's father defending his son's stance attracted 5 million views, with a chorus of critical comments.

"Can Horton — an adult himself, make a statement? Why does his father talk instead?" asked a user named Chelsea Xi Yanyan.

"If he comes to China, he'll be beaten to death", said another popular comment, while a user named Red Maple wrote: "He is white rubbish in the water and is toxic waste after he gets out."

One of the most widely shared images is of a statement translating to: "To be a decent person, don't be like Horton."

An Australian school principal in China with more than 1.7 million Chinese followers, David Gulasi, has also joined the nationalistic chorus, calling Horton "an idiot", questioning whether he thinks he is a god and saying "people should kick his arse".

Australian David Gulasi said Horton should have "shown respect to others". ( Supplied: Weibo )

Sun Yang earlier played on the nationalistic sentiment, saying he could personally accept criticism but "disrespect towards China is very unfortunate".

The online commentary is in contrast to China's state media outlets, which have largely avoided editorials about Horton — a contrast to the last time the dispute flared up, at the 2016 Rio Olympics.

China's Foreign Ministry too avoided directly weighing in, with a spokesman saying the dispute is "not a diplomatic issue", and noting it should be handled by swimming officials, who have since warned Horton over his podium protest.

In Australia, popular WeChat Chinese media outlets have taken Sun's side, with one, Sydney Today, thundering "Australia's Horton, you don't have to respect Sun Yang but please respect China!".

Another flare-up between the pair has been avoided with Horton failing to qualify to face Sun in the 800 metre final on Tuesday evening.