What started as a bitter rivalry may have escalated into an international incident after Sun Yang accused Australia's Mack Horton of disrespecting China in a stunning podium protest at the world swimming titles in South Korea.

Olympic champion Horton refused to shake hands with Sun or stand on the podium after being relegated to 400m freestyle silver by the controversial Chinese star at Gwangju on an unforgettable opening night of the eight-day titles on Sunday.

It remains to be seen if Horton faces sanction from world body FINA over his protest.

Horton made the bold statement after admitting he was unhappy that Sun had been allowed to compete at the world titles ahead of a Court of Arbitration for Sport hearing in September that may end the Chinese star's career.

The 10-time world champion will answer charges of smashing vials of his blood with a hammer during a clash last year with testers.

Sun - who claimed a fourth straight 400m world title - faces a lifetime ban if found guilty.

Horton copped vile social media abuse while the Chinese swimming team demanded an official apology after he dismissed Sun as a "drug cheat" ahead of the Rio Olympics.

Their feud only escalated after Horton upset Sun - who served a three month doping ban in 2014 - to claim a shock 400m freestyle gold at the 2016 Games.

But it may pale in comparison to the fallout over Horton's latest actions, with three-time Olympic champion Sun claiming his protest was an 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'm aware of the rumours (about his alleged hammer attack).

"(But) I think this has been the greatest achievement in history for the Chinese (swimming) team."

The Australian team's reaction to Horton's stance will no doubt further infuriate Sun with the Dolphins throwing their support behind the 23-year-old.

Head coach Jacco Verhaeren claimed he had no prior knowledge of Horton's protest but had no problem with it.

"That was his idea to do that. But let's put it this way, I understand him very much," he said.

"He has been very strong and vocal about this in the past ... you can only respect him for what he does.

"Mack stands for what he stands for. Nobody can take that away from him, nobody should."

Dolphins team leader Cate Campbell - another vocal critic of Sun in the past - championed Morton's stand.

"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.

Australian Associated Press