The International Olympic Committee (IOC) supports freedom of speech but there should be a line drawn between freedom to speak and "trash talk".

When asked about how to distinguish between freedom of speech and trash talk, IOC spokesman Mark Adams said on Monday: "We support freedom of speech but on the other hand, at the Olympics it's also about respecting your rivals. There is a line somewhere between people should be free to speak and have respect for others."

The IOC comments followed the on-going row between Chinese and Australian swimming over Australian swimmer Mack Horton's unfriendly remarks, labeling Chinese swimmer Sun Yang as "drug cheat".

The Chinese swimming authorities wrote to its Australian counterpart demanding an apology from Horton for "his inappropriate comments" while the Australian side backed Horton saying: "Mack is entitled to express a point of view. Under the Team Values ASPIRE the E stands for express yourself, that is his right. He has spoken out in support of clean athletes. This is something he feels strongly about and good luck to him."

Sun, who won gold in the 400m freestyle and 1500m freestyle at the London 2012 Olympics, served a three-month ban in 2014 after using a banned substance which was added to the World Anti-Doping Agency drug list in 2014.

The 24-year-old said he unwittingly took the drug as part of treatment for a chronic heart problem.

After winning the 400m freestyle gold medal race here on Saturday, Horton said: "I used the words drug cheat because he tested positive. He's one of the athletes here who has tested positive."

Previously in practice, Horton said he ignored Sun who tried to greet him and said "I don't have time or respect for drug cheats."

The Australian's comments prompted a heated response on social media, where many Chinese fans described the remarks as unjustified.