Police are currently dealing with a serious incident which has closed the A47 at Tilney All Saint.
Emergency services were called to the scene at 3.46pm today following reports a child had fallen from a coach.
The boy has been taken to the Queen Elizabeth Hospital in Lynn with life-threatening injuries.
A number of other people were on board the coach at the time and no other passengers were injured.
The road is expected to remain closed for some time and local diversions have been put in place. It is closed westbound from the Pullover roundabout in Lynn.
Officers are keen to speak with anyone who may have witnessed the incident.
Contact police on the non-emergency police line, 101 (calls cost 15p).