Two men are in hospital after the motorised bicycles they were riding collided and burst into flames in South Grafton last night.

Shortly before midnight the two men, aged 25 and 41, were travelling west along Ryan Street, South Grafton, when their petrol-driven bicycles collided.

Flames engulfed both riders, with a passing motorists stopping to assist the men. Nearby residents were alerted by a passer-by, who used a garden hose to douse the flames.

The 41-year-old man sustained extensive third degree burns and head injuries and was early this morning critically ill in hospital.

The younger man suffered serious burns to his left leg, as well as lacerations to his head, and is understood to be in a serious condition.

Both men were initially taken to Grafton Base Hospital before being airlifted to the burns unit at Sydney’s Royal North Shore Hospital.

Officers from the Coffs/Clarence Local Area Command attended the scene overnight, with both bicycles seized for forensic examination.

Ongoing inquiries into the incident are being carried out by Ballina Crash Investigation Unit officers.

Anyone who witnessed the incident, and who has not already spoken with police, is urged to contact police via Crime Stoppers on 1800 333 000.