A man who fell badly while performing a motorcycle jump is believed to have suffered multiple leg fractures.

A Palmerston North Rescue Helicopter confirmed they flew the 23-year-old man to Palmerston North Hospital following the incident in the Pohangina Valley, north of Palmerston North.

The man was stabilised at the scene by the on-board St John Ambulance intensive care paramedic before being flown to hospital in a serious but stable condition.

A Central St John Ambulance communications' spokesman confirmed they attended the incident, but he did not have any other details.