Counter-terror police have searched two houses on the NSW mid-north coast as part of their investigations into Friday's Christchurch mosque shootings, including the home of the sister of accused gunman Brenton Tarrant.

Key points: The family of the accused Christchurch mosque shooter had been assisting police with their investigation

The family of the accused Christchurch mosque shooter had been assisting police with their investigation Police assured the community there was no current or impending threat related to the searches

Police assured the community there was no current or impending threat related to the searches The accused, Brenton Tarrant, was originally from Grafton, where he worked as a personal trainer

Officers descended on the property at Sandy Beach, near Coffs Harbour, early on Monday morning.

A short time later, they also searched a house at Lawrence, about 115 kilometres north.

"The primary aim of the activity is to formally obtain material that may assist New Zealand Police in their ongoing investigation," police said in a statement.

Mr Tarrant's family continued to assist with the investigation, they added.

"The community can be assured that there is no information to suggest a current or impending threat related to these search warrants."

Brenton Tarrant made a brief court appearance on Saturday morning. ( New Zealand Herald/Pool via Reuters: Mark Mitchell )

Fifty people were killed on Friday when Mr Tarrant allegedly opened fire at two Christchurch mosques.

He was originally from Grafton and worked as a personal trainer at Big River Gym.

Neighbour says accused was 'cold'

New Zealand police are also searching Mr Tarrant's apartment in the city of Dunedin, which is a five-hour drive south of Christchurch.

Specialist teams were spotted crawling through the bushes outside the building.

Some neighbours who live on the street have told the ABC they were shocked by Mr Tarrant's alleged role in the attack.

"He didn't walk around like a Nazi in camo," one man said.

"He dressed like a normal Joe.

"He didn't have parties, he always had his curtains drawn and he kept his garden neat."

Mr Tarrant's Dunedin home, where some neighbours said he was "cold". ( ABC News: Barbara Miller )

However, a woman who lives nearby said Mr Tarrant sometimes made her uncomfortable by staring at her when she walked by.

"I found him cold and would avoid his eyes," the woman, who did not want to be identified, said.

"I got goose bumps finding out he was a white supremacist."

Family in shock

In an interview with Nine News, Mr Tarrant's family expressed shock and apologised for his role in the shooting.

His uncle, Terry Fitzgerald, mourned the victims in Christchurch.

"We are so sorry for the families over there, for the dead and injured," he said.

Mr Tarrant finished school in 2009 and left the gym two years later to go travelling in Asia and Europe.

His former boss at the gym has described him as "very dedicated" and expressed disbelief that her former employee allegedly shot dead dozens of people at two mosques.

New Zealand Prime Minister Jacinda Ardern has said Mr Tarrant was not on any watch lists, while NSW Police said he was known in Australia only for minor traffic matters.

Officers descended on the Coffs Harbour property early on Monday morning. ( ABC News: Melissa Martin )

Ms Ardern has flagged changes to gun control laws in New Zealand in the wake of the shootings and her Cabinet will meet today to discuss tighter controls.

Five legally-obtained firearms were used during the attacks.

Gun control campaigners are lobbying for a ban on military-style semi-automatic weapons in New Zealand.

Mr Tarrant sent out a so-called manifesto about his alleged plans to more than 30 recipients, including Ms Ardern's office, prior to the shootings.

He was arrested within 36 minutes, Ms Ardern's office has said.

A preliminary list of the victims has been circulated to families and the process of returning bodies was expected to begin today.