Gwangju - Four-time Olympic medalist Chad le Clos has voiced his opinion over China's Sun Yang competing in this year's FINA World Championships in Gwangju, South Korea.

Sun is competing under a doping cloud after a leaked FINA report alleged he smashed blood samples with a hammer after being visited by testers last year.

The 27-year-old was also banned in 2014 for three months by the Chinese Swimming Association for doping.

Sun's appearance in South Korea has seen him face hostility from swimmers notably from Briton Duncan Scott and Australian Mack Horton, who shunned Sun during the 400m freestyle and 200m freestyle medal ceremonies.

WATCH: 'You lose, I win!' Sun rages at Scott over medals snub

Following his 200m butterfly semi-final race on Tuesday, Le Clos stated that he wanted to be upgraded from his second place finish at the Rio Olympics.

In 2016, Le Clos took silver in the men's 200m freestyle and lost in 0.55 seconds to Sun.

"It's good that people are taking a stand," Le Clos told in Gwangju.

"I want my gold medal back from Rio and (fourth-placed) James Guy should get his bronze, because it shouldn't be allowed to have people cheating in sport."

The South African swimmer has also been vocal and commented after Horton's medal ceremony snub on Sunday.

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Team South Africa have yet to bag a medal at this year's FINA World Championships.

Le Clos will be hoping to put South Africa on the medal tally as he competes in the final of the men's 200m butterfly on Friday.