Singapore's only male cyclist to win a medal at last month's SEA Games is now being investigated by police for assault.

National cyclist Vincent Ang, 38, allegedly slapped and hit a fellow national rider during a training ride on Sunday and later that same morning at Adam Road Food Centre, eyewitnesses told The Straits Times.

His alleged victim was fellow national rider Ang Kee Meng - the two men are unrelated. The 29-year-old declined to comment on the matter, but The Straits Times understands he has lodged a police report.

A police spokesman confirmed this, adding that they were looking into the matter.

On Sunday, both cyclists were part of a group of seven riding in a pace-line down Lim Chu Kang Road. A pace-line is a riding formation where cyclists take turns riding at the front to conserve energy .

Most of the riders were peeling off to the left after their turn at the front, except for a young rider and an older man who turned off to the right, said one cyclist in the group, who declined to be named.

Mr Vincent Ang yelled at the young rider for doing so and claimed that the rider had nearly clipped his front wheel.

"Vincent shouted at him and asked why was he so 'special' and going right when everyone was going left," said the cyclist. "Kee Meng came to the rider's defence. He told Vincent if he was not happy, he didn't have to ride with us."

The older Ang supposedly reacted by slapping his teammate on the back and later punching his helmet - all while the group was hurtling down the road at speeds exceeding 40kmh.

Later, when Mr Ang Kee Meng was having breakfast with about a dozen other cyclists at Adam Road, Mr Vincent Ang entered the hawker centre, hit the younger man in the head and challenged him to a fight, said eyewitnesses.

"It happened right in front of us. Kee Meng didn't retaliate," said cycling enthusiast Adam Han, 39, adding that cyclists there blocked the two men before they could come to blows.

When contacted, Mr Vincent Ang declined to comment. He said: "I have nothing to say to you."

On June 12, he won the bronze medal in the men's criterium - a multi-lap race around a circuit - at Marina Bay South, the only other cyclist besides Dinah Chan to manage a podium position.

The veteran cyclist has had his brushes with controversy.

In February, pictures of Mr Vincent Ang cycling with his two-year-old son in one hand and mobile phone in the other - all this while wearing the national jersey - were posted on citizen journalism website Stomp.

A month later, he was involved in an incident with a car driver who allegedly ran over his bicycle.

In the build-up to the Singapore SEA Games, Mr Vincent Ang had told The Straits Times that he was hoping to put these matters behind him.

"I hope to do well and use that as a rebound to start on a clean slate," he had said.

"A lot has happened in the past few months, and I admit I must share part of the blame, but I want to move on from this."

Singapore Cycling Federation general manager Mahipal Singh told The Straits Times that it was investigating the matter.

"The federation is looking into it and is concerned," said Mr Singh yesterday.

"It's an unpleasant incident, and depending on what we establish, we cannot condone such actions," he added.