Three people have been killed and another critically injured in a head-on smash near Muswellbrook.

Emergency services were called to Bengalla Road at Castle Rock just before 9.30pm on Sunday where a utility and a Kia Carnival people mover had collided.

Police say the driver and sole occupant of the utility – a man believed to be in his 30’s – died at the scene.

The male driver and a female passenger in the Kia also died at the scene,  while a fourth person, a man in his 60’s, was airlifted to the John Hunter Hospital with life-threatening injuries.

The victims are yet to be formally identified.

Investigators are still trying to piece together the circumstances leading up to the crash and a report will be prepared for the Coroner.