Child found dead, two more critical after stabbing

A young child has died and two others are fighting for their lives after a stabbing attack.

Emergency services responded to reports three children and a woman had been found with stab wounds in a vehicle on Waratah Rd at Valley Heights, a small township in the NSW Blue Mountains, about 12.45pm on Sunday.

Officers were told members of the public performed first aid on the woman, believed to be in her 40s, and children while contacting the authorities.

One of the children was found dead inside the vehicle, while paramedics treated the remaining two children and woman at the scene.

The two children and woman were taken to Westmead Children's Hospital and Westmead Hospital, respectively, all in critical condition.

Police said their identities are yet to be confirmed, but the children were all thought to be younger than five.

A crime scene has been established, but authorities said they were not looking for anyone else in relation to the incident.

Anyone with information about the stabbing or who had footage of the attack is urged to contact police.