The cyclist was taken to hospital with "nonlife-threatening" injuries.
"The driver continued to flee. However, the pursuit was immediately abandoned and officers stayed with the injured cyclist as other patrols went into search mode to see if the vehicle could be located," Mr Harrison said.
"We don't know where he went after that - we lost sight of him for some time."
Police did not know how the driver ended up back in Wanganui when he was last seen heading out of town, but he was spotted a short time later in Rapanui Rd and police had begun setting up road spikes.
Mr Harrison said there were "lots of police staff out there in their vehicles", which meant they were in the right place to set up the spikes.
The driver had smashed into a culvert trying to avoid one set of spikes, and had then accelerated away for another two kilometres to where police had laid out more spikes.
"In a further attempt to avoid the spikes, the vehicle has driven into a large truck which was stationary on Tayforth Rd," Mr Harrison said.
"The car caught fire and the driver died at the scene. The driver of the truck is shaken but not injured."
Mr Harrison said the truck driver had been going along Tayforth Rd when he had seen the police laying down spikes, so he had pulled over to avoid them and "watched it tragically unfold, poor man".
Mr Harrison didn't know if there had been time for police to warn the truck driver to move away from the spikes, and noted "how quickly these things unfold".
"Just in the blink of an eye life can change forever."
Several specialist police staff, including CIB, were conducting a scene examination.
An investigation into the circumstances of the incident and an investigation into the pursuit would be carried out.
The Independent Police Conduct Authority had been informed.
Mr Harrison said police should be in a position to release the driver's name today.
A Tayforth Rd resident saw the speeding car go past, "straddling the white line, almost on the wrong side of the road".
The witness, who did not want to be named, said the car's rear bumper was hanging off, "flapping in the breeze".
He did not see the crash, but heard "the boom".
"Four police cars passed shortly after ... I figured they had a handle on it," he said.
Great North Rd resident Lachie Cromar heard a crash and came out to see the injured cyclist lying on the street.
"He was just lying in the gutter," Mr Cromar said.
The cyclist, in his early 30s, was discharged from hospital yesterday.
