Ponsonby Rd on the first day of the lockdown in New Zealand.

Police officers now have the power to enter homes to enforce self-isolation rules.

New Zealand entered a four-week lockdown to break the transmission of coronavirus on Thursday. Overnight, police officers have pulled over people who were breaking the self-isolation order — apparently unaware it was in place.

Police Commissioner Mike Bush, in a series of radio and TV interviews on Thursday morning, reiterated people will initially see the "friendly face" of police during the lockdown.

KEVIN STENT/STUFF Mike Bush, Commissioner of Police, says officers have alreayd come across people not complying with the lockdown.

​"But we'll be ensuring people will comply because if they don't, people will die," Bush said on RNZ.

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He said police already had to educate people on the self-isolation order overnight, and would continue this informative approach unless people intentionally flout the rules.

DAVID WHITE/STUFF An empty Auckland motorway on day one of the coronavirus lockdown in New Zealand.

Police officers would first issue a warning, then arrest people if needed. Bush said police would only prosecute serious offenders, but those arrested will be "having a little trip to our place" — meaning they will be detained.

"The public want that, they want people to comply because they're really worried."

He said it would "pay" for people to carry workplace identity cards, or letters from employers, to prove they were an essential worker.

A nationwide state of emergency was declared on Wednesday, giving police wide ranging powers. Under the Civil Defence Emergency Management Act, police can enter any premises under the belief it would save lives or prevent injury.

"If we suspect there are gatherings inside places, we're enabled to go in there. We'll do everything we can to make sure people comply," Bush said.

He said police would be monitoring activity around the country, and would "deploy" to areas that showed increased activity. There were several hundred soldiers ready to assist police with foot patrols, if required.

While roadblocks were not in place and were not planned, Bush said such a measure could be used if there were areas in which many people did not comply. People could expect to be pulled over and questioned, however.

Bush said there "could be" an increase in dishonesty crime, like theft, and there would definitely be an increase in domestic violence — "we'll be deploying into that with urgency".