KAZAN (Russia) • Mystery surrounded the conclusion of swimming's World Championships on Sunday, when China's twice champion and favourite Sun Yang did not show up at the starting blocks for the men's 1,500m freestyle final despite having warmed up for the race.

As Italian Gregorio Paltrinieri celebrated his first world title after winning the race in a European record 14min 39.67sec, the sport's governing body Fina said a chest complaint had caused Sun to pull out minutes before the start, denying him the chance to claim his third title of the week.

"I feel very sorry that I couldn't be present," Sun said later. "I didn't feel good in my heart. I felt really uncomfortable at the pool during my warm-up and I had to give up the idea of competing. It is the first time I have felt uncomfortable in competition."

Paltrinieri was shocked by Sun's absence. "I never saw him today," the Italian said. "We were speaking yesterday that the race would be a nice one. It was really disturbing to swim without him."

Whether Sun's withdrawal had anything to do with allegations that he tried to elbow and kick a female swimmer in the morning is not clear.

Brazil's coach Alberto Pinto da Silva told Brazilian sports news website globoesporte.com that the incident occurred when Larissa Oliveira was warming up alongside the Chinese swimmer in the pool.

"He was warming up and he pulled the Brazilian girl's foot," said the coach. "He ran her over. She got angry and had it out with him. He tried to elbow her and kick her.

"So then the Brazilian coaches went to speak to him. He said she was bothering him and one of the coaches said that the pool wasn't just his. Everyone was at the side of the pool, and they were all swearing at each other.

"There were about 15 people right up at him. But there wasn't any violence."

The website reported the Brazilian Aquatic Sports Federation later made a formal complaint to Fina.

When asked about the incident, Sun, who became the first Chinese man to win an Olympic swimming gold medal when he took the 400m and 1,500m freestyle double at London 2012, said: "I have no comment because it was a morning problem".

Da Silva also said that other coaches had gone to him with similar complaints about Sun.

"The Canadian (coach) came over to me and said, 'he has already bothered my swimmers'," da Silva said. "The South African (coach) said he bothered the swimmers when they were swimming. Chile, Argentina, everyone came to tell me what to do. If he's doing that to everyone then he's a dangerous guy, he has no place in sport."

Chinese swimming officials could not be reached for comment.

Sun, who was named the meet's top male swimmer after winning the 400m and 800m freestyle titles and finishing second in the 200m, had been "very upset and aggressive" in the locker room, according to a fellow competitor.

A Danish swimmer, who did not want to be named, said there had been a huge commotion with the Chinese delegation and that Sun had been agitated watching the 1,500m final on television in the locker room.

Sun, 23, has made just as many headlines away from the sport as he has in the pool. He was banned by Chinese swimming authorities in 2013 after being jailed for crashing a car he had driven without a licence.

It also emerged last year that Sun had secretly served a three-month ban after testing positive for a banned stimulant. The China Anti-Doping Agency could have imposed a longer ban but opted for a lenient punishment.

REUTERS, AGENCE FRANCE-PRESSE