Sporting nations should up the fight against racism ahead of the Olympics to avoid a repeat of extremist incidents at the Euro 2012 football championship, a UN expert said on Tuesday.
Racism is still a "serious problem" in sport, as shown by the behaviour of some fans, said United Nations special rapporteur on racism Mutuma Ruteere.
He called for extra measures before the London games begin on July 27.
"Neo-Nazi symbols, slogans and banners displayed during football matches and racist monkey chants directed at players or supporters should not be tolerated," he said in a statement to the Human Rights Council.
"I call upon states to intensify the fight against racism in sport and to strengthen the role of sports in promoting cultural diversity.
"In particular in light of the upcoming Olympics it is crucial that further preventative measures be taken to avoid racist incidents during this event."
Football governing body UEFA fined Russia, Spain and Croatia over fans' racist chants during matches in the Euro 2012 championship.
UEFA president Michel Platini has repeatedly insisted that the organisation operates a "zero-tolerance" policy towards racism in European football.
Questioned on what action could be taken to avoid repeat scenes at the Olympics, Ruteere said he was talking about pre-emptive measures.
"These include creating awareness among communities... and ensuring that different people are actually benefiting from events like the Olympics," he said.