A national serviceman is in critical condition after suffering serious head injuries following an accident during the OCBC Cycle Singapore on Sunday.

Mr Chia Wee Kiat, 24, was involved in a crash on Benjamin Sheares Bridge soon after the 5.15am start of the 59km Super Challenge which he was participating in.

It is unclear how Mr Chia was hurt. But event organisers have said on their Facebook page that they are currently contacting witnesses, as well as the Land Transport Authority, to obtain more information of the accident.

Organisers said that they were notified of the accident at approximately 5.39am and a fast response motorbike paramedic attended to Mr Chia within six minutes. He was then sent to Singapore General Hospital by an ambulance and arrived there at 6.14am.

However, eyewitnesses who were at the scene said it took about 20 minutes for help to arrive.

The annual OCBC Cycle Singapore attracted more than 11,500 participants this year. It was organised by Spectrum World who are also the event owners.

Said Ms Koh Ching Ching, head of group corporate communications, OCBC Bank, who are the event sponsors: "The safety of the participants of the event is of paramount importance to us.

"Every year, we work closely with Spectrum to ensure that all safety aspects of the event are thoroughly considered and that measures are put in place to ensure the safety of all participants. We want all participants to enjoy the ride and be safe.

"It is with heavy hearts that we work closely with Spectrum to get the details surrounding the accident. Together with Spectrum, we are extending help to Mr Chia's family where it is needed. We wish Mr Chia a quick and complete recovery."