The police say a serious knife attack on an officer by a highly agitated man in Auckland on Monday morning was so sudden that there was no chance for other officers to help him.
Acting district commander, Inspector Jim Wilson, says Constable Todd Martin was stabbed once in the face with a long-bladed knife in Orakei shortly after 10am.
Mr Wilson says Mr Martin, 47, was responding to reports that a man on a bicycle had been threatening and abusing people.
Mr Wilson says two other police officers had a taser but Mr Martin was attacked so suddenly that they had no time to react.
He says Mr Martin's injuries are not life-threatening but he's had to have surgery at Auckland Hospital.
A 38-year-old homeless man was arrested at a block of apartments on Patteson Avenue in Mission Bay less 30 minutes later.
Witnesses say the man struggled against the police and had to be tasered before they could arrest him.
The police say he is being assessed by mental health specialists.
He will appear in Auckland District Court on Tuesday to face three charges of assault with a weapon, and one charge of wounding with intent to cause grievous bodily harm.
The police have failed to find the knife and are asking the public to call them if they find the knife or any other suspicious items.
The Police Association is renewing its calls for police to be armed after the incident.
President Greg O'Connor says attacks on police often happen with no warning and during seemingly minor incidents.
"Because these incidents almost invariably arise from ordinary pieces of policing, it's important that the police officers have the right equipment to deal with them at the time. And that means having a taser on the hip and unfortunately it increasingly means needing a firearm on their hip as well."
Mr Wilson says other officers at the scene were armed with a taser but had no time to use it during the sudden attack.
"When the knife was drawn he also started to walk down to the other two officers as well in a threatening manner; threatening them with the knife so they backed off. There was no time for the taser to be deployed at that stage."