A husband and wife have been killed and their son is in a critical condition after a car which had earlier been involved in a police pursuit crashed into their vehicle in Perth's northern suburbs.

Police attempted to stop the car on Saturday night after it was reportedly being driven erratically and at high speed.

Officers engaged in a pursuit on Warwick Road in Warwick about 7:30pm but called it off after the car continued to be driven at high speed.

A short time later it crashed into a family's car near the intersection of Warwick and Ballantine roads in Greenwood.

A 60-year-old woman died at the scene and her 66-year-old husband died later in hospital.

Their 25-year-old son, who was driving the family's car, is in a critical condition with life-threatening injuries.

Sorry, this video has expired Police say the driver "failed to stop and accelerated at a high speed".

It is alleged a 16-year-old boy in the car that evaded police fled the scene.

He was apprehended nearby and is now in custody. No charges have yet been laid.

An 18-year-old female passenger was found inside the vehicle by police officers. She was taken to Royal Perth Hospital.

Police at this stage believe the boy was driving the vehicle but have not yet confirmed that as part of their investigation.

Deputy Police Commissioner Stephen Brown expressed his sympathy to the family and friends of the victims.

"Can I express my deepest sympathy to the family of those who were killed and also seriously injured last night (Saturday) in what can only be described as a tragedy," Deputy Commissioner Brown said.

He said from what he understood, the two police officers who engaged in the pursuit were following protocol.

"On the basis of information known to me at this point, the officers had good reason for attempting to stop that vehicle," he said.

"It appears the officers have followed the policy, but of course that will be the subject of a comprehensive investigation."

Police said both the 16-year-old and 18-year-old were known to police and the vehicle was registered to a person related to the boy.

An arrest warrant had previously been issued for the boy for an alleged breach of bail on another matter.

He is set to face court on Monday over that separate charge.

Major Crash Investigators and officers from the Internal Affairs Unit are investigating.