FOUR people have died and two people were left injured after two crashes near Muswellbrook on Sunday.
A crash on Bengalla Road about 9.30pm claimed three lives after two cars, a Kia Carnival and a utility, collided head on.
Police said the utility's driver and sole occupant, a man believed to be aged in his 30s, died at the scene.
The Kia's male driver and female passenger are yet to be formally identified after they also died at the scene.
Police said their ages are unknown.
A third occupant of that car, a man believed to be in his 60s, was flown to the John Hunter Hospital.
Police described his injuries as life-threatening.
Hunter Valley police established a crime scene and are investigating the circumstances of the crash.
A report will be prepared for the coroner.
Separately, a woman died in a crash on Allyn River Road after a Toyota Landcruiser reportedly rolled down an embankment and crashed into the river.
Police said a second woman, the vehicle's driver, was also injured in the crash, which occurred just after 11am on Sunday about 50 kilometres east of Muswellbrook.
"Witnesses climbed down the embankment and freed the female passenger from the vehicle, before commencing CPR," NSW Police said in a statement.
Paramedics arrived and rendered assistance but the woman died at the scene. She is yet to be formally identified.
The 18-year-old driver was able to free herself from the vehicle after the crash.
She was winched from the river area and flown to the John Hunter in a stable condition.
Port Stephens Hunter police set up a crime scene and commenced an investigation into the circumstances around the incident.
Anyone with information about either crash is urged to call Crime Stoppers on 1800 333 000.