An unarmed New Zealand policeman was shot and killed on an Auckland street Friday, becoming the first officer to die on duty for more than a decade in the normally peaceful South Pacific nation.

Police said the officer and a colleague were approaching a crashed car when a gunman produced a rifle and opened fire.

One officer died, another received serious leg injuries and a bystander was struck and badly hurt as the two men drove off in a second car, New Zealand's police commissioner Andrew Coster said.

He said two persons of interest were being questioned after being apprehended several hours later following a massive manhunt which also resulted in police seizing a firearm.

"This is a shocking situation. It is the worst news that police and police officers' families can ever receive in the course of what we do," Coster said. 

"Our officers walk towards danger every day, our job is to keep them safe."

Prime Minister Jacinda Ardern offered condolences to the officer's family and police colleagues.

"This is devastating news. Our police officers work hard every day to keep us and our communities safe," she said.

The slain policeman, whose details have not been released, is the 23rd to be shot dead on duty since 1890, according to the police website, with the previous fatal shooting in 2009.

Coster declined to speculate on a possible motive for the shooting.

"This was the type of work that our officers undertake every day to keep the public safe," Coster told reporters, adding "the situation unfolded very quickly".

"At this stage, there is nothing to indicate that this job was going to be anything out of the ordinary."

No charges had been laid by late Friday and Coster said the priority "is to hold this offender to account".

Coster said the officers were unarmed when they came under fire, which is standard for New Zealand police.

The force last week decided against introducing armed patrols and Coster said the shooting would not prompt him to revisit the issue.

However, he said police on duty in the west Auckland suburb of Massey where the shooting took place would be issued firearms for the time being as a precaution.

The death comes just a day after parliament voted to further tighten New Zealand's firearms laws in the wake of last year's Christchurch mosques massacre, when a lone gunman murdered 51 Muslim worshippers.