A woman has appealed for help to locate a cyclist who knocked down her three-year-old son at a park connector on Sunday morning.

Housewife Kaslyn Tan's Facebook post has gone viral, garnering more than 10,000 shares since it was uploaded on the same day.

The boy had to be taken by ambulance to KK Women's and Children's Hospital for treatment of his injuries, which included bruises, loose teeth and a cut on his chin that required stitches, said Ms Tan, 25.

The incident took place on a shared path for pedestrians and cyclists along the Serangoon Park Connector at around 11.15am.

Police said a report had been lodged over the incident and they are investigating.

Ms Tan, who questioned in her post the need for the cyclist to ride at such "lightning speed", said the cyclist had dismounted and apologised to her husband, air force engineer Lin Jian Xiong.

Mr Lin, 32, was alone at the time with their son, Kyle.

He told The Straits Times that they had just finished their jog and were heading for breakfast. Kyle had been walking about 2m ahead of him when he spotted a nearby fitness corner and changed direction abruptly to cut across the path.

The cyclist, who was approaching from the opposite direction, noticed Kyle only at the last moment and attempted to swerve to his left to avoid a collision.

"His bike's right handle connected with my son's lip. Kyle lost a tooth from the crash and he was covered in blood," said Mr Lin, who estimated that the cyclist had been travelling at 30kmh to 40kmh before he shouted at him to stop.

"He (the cyclist) later told me that his feet were clipped to the bike's pedals and he had no brakes, when I asked why he did not stop."

According to Ms Tan, the cyclist initially gave her husband $10 for medical expenses but later offered another $20. He then left without leaving his number.

"I was still in shock from the accident and was focused on stopping Kyle's bleeding, so I forgot to ask for his contact details," Mr Lin explained. He took Kyle home to his wife before they decided to call 995 for an ambulance as they were told that a non-emergency ambulance would take too long to arrive.

Ms Tan's post also contained a plea for help to locate the cyclist so that the family could have a "peaceful closure".

Ms Tan described the cyclist as a 1.65m-tall man who appeared to be in his 40s. He was clad in cycling gear and said he lived in Pasir Ris, she added.

In subsequent updates on the same post, she also spoke about her son's condition after returning from the hospital, and thanked the National Parks Board (NParks) and Singapore Police Force for their help.

Her son, she said, was unable to eat, sleep or talk properly due to the pain and swelling. An X-ray found no bone damage, but he would have to return to the hospital for check- ups and to remove his stitches.

He will also see a dentist about his shaky teeth caused by the collision.

Mr Lin and his wife stressed that their aim was not to denounce the cyclist. "We want to raise awareness of this incident to the public and urge everyone - not just cyclists - to use the paths responsibly. It could happen to anyone," he said.

Ms Tan said she received a call from NParks yesterday morning. It assured her that it would be working closely with the police and the Ministry of Transport to enhance safety on foot and cycling paths at park connectors.

In a statement to The Straits Times, NParks director of parks Chia Seng Jiang said it had contacted Ms Tan and was working with the police to identify the cyclist.

As the park connector network caters to different recreational activities, Mr Chia advised users to keep to the left of the shared track while reminding cyclists to keep a lookout for pedestrians.

"NParks has also been working with the cycling community to promote responsible cycling through regular workshops and bike clinics," he added.