Furious supporters of Chinese swimmer Sun Yang have threatened to kill Australian long-distance swimmer Mack Horton and his girlfriend in response to his world championship protest against the alleged drug cheat.

A barrage of online threats and abuse, many of a violent nature, came just hours after second-placed Horton refused to share the podium with victorious Sun following the 400-metre final at the World Aquatics Championships in Gwangju, South Korea.

“This is going to continue to brew over the next 12 months.”

Tensions were high on the men’s 400m free podium, Australian Mack Horton refused to stand next to Chinese swimmer Sun Yang who's facing allegations of doping rule violations that could result in a #Tokyo2020 ban pic.twitter.com/9QN1VfUln7

— CBC Olympics (@CBCOlympics) July 21, 2019

By 3pm Monday the opening post on Horton’s Instagram page had attracted almost 12,500 comments, the vast majority taunts and threats.

An example of the violent threats made against the Australian swimmer on social media.

Horton was called a “fat Aussie pig”, “pathetic loser”, “retarded” and “disgusting” in a range of abusive comments, along with more violent threats against his family.

Pictures of Horton with his girlfriend, childhood sweetheart Ella Walter, attracted death threats, and comments of a violent and sexual nature, which The New Daily has chosen not to repeat.

This photo of the couple at Flemington Racecourse attracted death threats from supporters of Sun Yang. Photo: Instagram

Horton also refused to shake the hand of Sun following their race in South Korea on Sunday.

Sun has been charged with smashing vials of his blood with a hammer to prevent doping testers taking samples at his home in China.

The three-time Olympic champion, who has now won the last four 400-metre titles, faces a lifetime ban from swimming if found guilty.

Sun responded to Horton’s actions by claiming his protest caused offence to China.

“I was aware that the Australian athlete had dissatisfaction and personal feelings towards me,” Sun said via an interpreter.

“But it was unfortunate because disrespecting me is okay but disrespecting China was very unfortunate and I felt sorry about that.”

“I think this has been the greatest achievement in history for the Chinese [swimming] team.”

This photo of the couple had attracted almost 12,500 comments by 3pm Monday. Photo: Instagram

But Horton’s protest drew widespread support from other swimmers. American champ Lilly King said the Australian received a standing ovation on his return to the athletes’ village on Sunday.

“We were kind of waiting around for that awards ceremony to see what was going to happen and yeah it was awesome,” two-time Olympic gold medallist King said.

“The whole dining hall erupted in applause, so it was pretty great to see the athletes united on his stance and supporting him as well.

“I don’t think anyone at FINA is going to stand up for the athletes so the athletes have to stand up for themselves.”

Australian officials spoke with world body FINA on Sunday night and were assured Horton would not face sanctions for his protest.

His act received praise, however, from his supporters and teammates, including Dolphins captain Cate Campbell.

“I support clean sport and I support swimmers standing up for their beliefs and I think that Mack did an incredible job and we’ll take it as a win for Australia,” she said.

It’s not the first time the Horton and Sun have clashed publicly. Horton labelled Sun a “drug cheat” after a rare win over the Chinese champion in the 400-metre freestyle event at the 2016 Rio Olympics.

Horton’s father Andrew, speaking to radio station 3AW on Monday, said his son meant no disrespect to China, but was taking a stand in support of consistency in the testing regime from FINA, the body overseeing international swimming.

“I think he was frustrated and disappointed, as so many of the athletes are, that this issue has tagged along into world championships.”

Mr Horton said his son’s stance had “absolutely” caused consternation in China “but I think it’s really important that we’re very much on the record that this is all to do about the process of swimming and ensuring there’s a fair process of swimming”.

“It’s not a commentary about China, we have huge respect for China.

“This is about ensuring that there are systems and processes in the sport that keep the sport clean.”

Swimming Australia has been contacted for comment.

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-with AAP