Mother confirmed as suspect in domestic violence stabbings

A 42-year-old woman is being treated as a suspect following the stabbing of three children on Sunday.

One child was found dead in a car parked at Valley Heights, while the mother and two younger children had serious stab wounds.

The woman and two children remain in hospital in a critical condition.

The death of a five-year-old boy, and the stabbing of two other children in the Blue Mountains is being treated as a domestic violence incident, police have confirmed.

Emergency services were called to the scene at Valley Heights near Springwood about 1pm on Sunday after walkers discovered the group of four in a parked car.

The five-year-old boy died at the scene, while two younger children and a 42-year-old woman were found with stab wounds.

They underwent surgery and remain in hospital in a critical condition.

NSW Police Deputy Commissioner Peter McKenna said all children were siblings, with their mother now a suspect in the domestic violence-related matter.

"I can state that the female is the mother of all three children and is a suspect," he said.

Deputy Commissioner McKenna said the four were found in what appeared to be a "random" location, and investigations into the incident were ongoing.

The incident followed three other alleged domestic violence-related deaths in NSW over the weekend.

Police say two women, aged 90 and 23, were fatally stabbed in separate incidents at homes in Bondi Beach in Sydney, and Kooringal in Wagga Wagga .

A third woman, aged 70, was found dead at a property in the state's Northern Tablelands region.

Deputy Commissioner McKenna said the community had been heavily affected by the incidents.