Three teens died in a Christchurch crash after fleeing police - and officers needed medical treatment after attempting to rescue them from the burning vehicle.

It has also been confirmed the teens were in a stolen car that crashed into a tree, dislodging the fuel tank, which then ruptured and erupted into a "ball of fire".

Canterbury district commander Superintendent John Price told a press conference this afternoon that the vehicle had run over road spikes and then crashed into a tree, bursting into flames.

"This is absolutely a tragedy," he said.

The stolen car was travelling in excess of 130km/h through city streets before road spikes were laid and the crash occurred.

Prior to the crash, the car had been involved in a pursuit with police for about one minute, Price said.

The first officers at the crash scene needed medical treatment after trying to free the trio from the burning car.

"They attempted to rescue the driver and the passengers from the vehicle, but sadly this was not possible due to the intense heat and fire."

Price, who visited the scene last night, said a disaster victim identification team would now go through the process of formally identifying the people in the car.

He had spoken to the officers involved and said they were 'absolutely devastated about what happened".

'Ball of fire': witness

Nearby resident Ruth Maxwell told Newstalk ZB she missed the crash by seconds.

"[There was] a loud whooshing sound ... [I] looked out the window and saw the flames, couldn't see much but a ball of fire. No one got out of the car."

The car was stolen and the three killed were the driver, 16, and two boys aged 13, Stuff reported.

Police arrived soon after and quickly put up tents, she said.

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

The three were killed when their car struck this tree.

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

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

Police laid spikes in an attempt to stop the vehicle.

The vehicle hit the spikes and crashed into a tree on Blenheim Rd outside a group of shops, catching fire.

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

Spate of fatal pursuits in Christchurch

The fatal crash following a police pursuit was the third in Christchurch in less than two months.

Alexia Noble-Hazelwood, 18, was killed when the car she was in smashed into a school building on Gloucester St, late on November 16, a Friday night.

The car had earlier been involved in a police pursuit which was abandoned just minutes before the crash.

In the early hours of Wednesday, December 5, driver Dennis Tunnicliffe, 25, and passenger Renee Percy, 35, a pregnant Christchurch mother, were killed after Tunnicliffe sped away from police before crashing into a power pole on Breezes Rd.

Police followed the car after Tunnicliffe fled but abandoned the chase after less than a minute due to the "dangerous nature of the driving".

A real tragedy

Price said last night's triple-fatal crash was "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."

Police Association president Chris Cahill it was a "real tragedy" that would have been "unforeseen" when laying the road spikes.

"Our thoughts go out to their families, it is a real tragedy. Even more tragic is it was avoidable, just don't drive in that manner."

Early reports suggested officers involved had "done everything right".

"They have withdrawn from the fleeing driver when they realised they were not going to stop, then used road spikes to try and deflate the tyres to slow the vehicle down.

"The results here are unforeseen, but if they hadn't taken that option and they continued to drive at that speed they posed a danger to the public."

Cahill said reports the driver and passengers were teenagers was a "real concern".

"It is all too common. [Teenage drivers] is an issue for police, they don't know who is driving the vehicle and they have got to react to what is in front of them."

Since July 2017 the Independent Police Conduct Authority and New Zealand Police have been reviewing fleeing driving events to "better understand the fleeing driver environment and police management of these events".

The report was intended to be finalised and made publicly available in late 2018, but has been delayed until February 2019.

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

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