The swimming rivalry between China and Australia has escalated beyond the pool, with Australian swimmer Mack Horton's comments about Chinese rival Sun Yang triggering heated confrontations.

The feud was first stirred up by Horton before the men's 400m freestyle final at the Rio Olympics, when he called Sun a "drug cheat" during a poolside interview. It then intensified when he used the term again after edging out defending champion Sun to win the 400m gold medal on Saturday.

Regarding his remarks, Horton, who was beaten by Sun at last year's world championships in Russia, said he didn't intend to single out Sun.

"I used the words 'drug cheat' because he tested positive. It's not specifically made about Mr Sun. I just have a problem with athletes who tested positive and are still competing," the 20-year-old said at the post-final news conference with Sun beside him.

Horton's comment caused an outrage among Chinese netizens as thousands of Chinese social media users demanded that Horton apologize to Sun.

After testing positive in March 2014 for trimetazidine in medication he had taken for treatment of a heart condition, Sun was banned for three months by the Chinese Swimming Association. He provided adequate proof at a hearing that the substance was used for a medical reason and not to enhance his athletic performance, according to the China Anti-Doping Agency.

Sports sociology expert Lu Yuanzhen at South China Normal University said that although Sun should be held accountable for his mistake two years ago, accusing an opponent face-to-face who has served out his suspension and retested clean shows no grace or respect, which rarely happens at major international events.

"Anyone who suspects others of doping should report it to responsible authorities like the World Anti-Doping Agency. But an athlete is not in the position to make such a strong statement against another without knowing what really happened," he said.

The Chinese Swimming Association on Sunday sent an official letter to Swimming Australia, the sport's governing body in that country, demanding an apology from Horton for his "inappropriate remarks, which have hurt the feelings between Chinese and Australian swimming circles".

In a statement issued on Sunday evening, the Australian Olympic Committee backed Horton.

"Mack is entitled to express a point of view. He has spoken out in support of clean athletes. This is something he feels strongly about and good luck to him," said the statement.

Sun avoided firing back at the news conference, saying only that he has proved he is clean and every athlete making it to the Olympics legitimately deserves respect.

Sun and Horton will face each other again in a highly anticipated 1,500m freestyle final on the last day of the Rio Olympics' swimming competition on Sunday.

"What happened yesterday stays yesterday. Now I am fully focused on preparation for the 200m and 1,500m. Hopefully I can achieve good results as expected," Sun said on Monday after clocking 1 minute and 45.75 seconds, the world's best mark this year, in the 200m semifinals to reach the final on Tuesday.

sunxiaochen@chinadaily.com.cn