New legislation for tighter gun controls would be introduced to Parliament next week, Prime Minister Jacinda Ardern said this afternoon.

The Government last week announced it would ban military-style semi-automatics and assault rifles.

The country's rules around guns have been in the spotlight since this month's mosque shootings in Christchurch.

In response to other questions this afternoon, Ardern said the police may not have had the detail required to track the gunman's movements immediately.

There have been criticisms of how the gunman managed to travel from one mosque to another without being apprehended.

Ardern added that there will be an investigation into the first responders in time, but the focus for now is to allow police to complete its investigation.

The investigation would not be a Royal Commission of Inquiry, but she will take advice on the nature of the investigation.

On Facebook, Ardern said she was pleased that white nationalism and separatism would be banned on Facebook, but conversations with other global players was still needed.

Ardern said her focus was on tomorrow's national remembrance service.

She said the focus should be on the Muslim community, and the service will reflect that. She will also address the domestic and global challenges including the fight against racism and hatred.

Australian Prime Minister Scott Morrison and leader of the opposition Bill Shorten will attend tomorrow's service.

Ardern will have a bi-lateral meeting with Morrison after the service.

She said 59 countries would be represented at the service, as would the UNHCR. Many heads of state from the Pacific community would also attend.

Ardern said Prince William would visit Christchurch in late April.

She said it was up to Prince William whether his family would travel with him to Christchurch.

Prince William also visited Christchurch after the devastating earthquake in 2011, and had a close affinity with the city.

She said there had been a significant response to people wanting to have a remembrance service in their communities.

Ardern said it was positive that Facebook would introduce tighter restrictions on harmful content, including on white nationalism and white separatism, which she said should arguably have been included from the beginning.

A global strategy would be needed to combat hate speech, Ardern said.

On Monday Cabinet agreed a Royal Commission would be set up to investigate how the attack was able to happen.

Cabinet agreed last week that there would be an inquiry to look at the specific circumstances leading up to the terror attack on March 15 and the role of agencies.

A Royal Commission is reserved for the most serious events.

Ardern said on Monday New Zealanders and Muslim communities around the world were "quite rightly" asking questions on how the terror attack was able to happen here.

The inquiry would look at the accessibility of semi-automatic weapons, the role social media played generally and the focus of the intelligence and security services.

The inquiry would look at what could have or should have been done to prevent the attack.
It would look at the alleged gunman and his activities before the attack.

It would look at the SIS, GCSB, Police, Customs, Immigration and any other relevant agencies.

It would look at events leading up to the attack but not the immediate response. The work of first responders would be looked at separately, Ardern said.