Three people have died after a police pursuit in Christchurch overnight.

Canterbury district commander Superintendent John Price said the vehicle crashed after running over police spikes and crashing into a tree, bursting into flames.

The vehicle was seen speeding about 11.13pm in the CBD, Price said.

Police began a pursuit but it was abandoned "very quickly due to the manner of driving by the offending vehicle".

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"It is believed the car has continued to drive at speed on Blenheim Rd," Price said.

Police were not in pursuit of the vehicle at this stage but were laying spikes in attempt to stop the vehicle.

The vehicle hit the spikes and crashed into a tree, catching fire.

"Police officers immediately went to help those in the vehicle, however tragically all three occupants died at the scene," Price said.

"An outcome like this is the last thing police want to see.

"We now have families who have lost their love ones and our thoughts are with them during this difficult time.

"We are currently working to notify and support their next of kin, as well as supporting our staff involved."

These incidents were always extremely testing for police, Price said.

"They are fast-moving, unpredictable and high pressure situations that require quick judgments.

"Ultimately, police are here to protect our community. Our staff must strike a balance between the responsibility to protect life and the duty to enforce the law."

A thorough police investigation had commenced to establish the facts of what occurred and determine further action, including notifying the Independent Police Conduct Authority.