teenage boy has critical head injuries and is fighting for life after crashing his trail bike in northern NSW.

Around 6:30pm on Sunday emergency services were called to a golf course at Walgett, following reports the 13-year-old had fallen off his trail bike.

Police say he was riding with two other boys, aged 13 and 11, when he crashed.

He was treated on scene for serious head injuries and later airlifted to Westmead Children’s Hospital in a critical condition.

AAP