Police Commissioner Mike Bush said police will be doing everything they can to make it possible for gun holders to bring in their soon-to-be illegal weapons.
Gun holders are asked not to show up to police stations without contacting them first and the online registration would be preferred by police.
Bush said the vetting process has been tasked to police investigators in relation to the arrest of the man who killed the 50 Muslims at the Christchurch mosques.
The Police Commissioner understands there are at least 250,000 firearms owners in New Zealand.
Police and a number of security agencies throughout New Zealand will continue to monitor how long the nation will be under a high level security threat but when changes are made, the country would be advised.
Bush expressed he was "hugely proud" of the officers who arrested the gunman, putting the "safety of the public before their own".
Military style semi-automatics and assault rifles will be banned in New Zealand under stronger new gun laws announced today.
"All semi-automatic weapons used during the terrorist attack on Friday 15 March will be banned," Prime Minister Jacinda Ardern said.
"I strongly believe that the vast majority of legitimate gun owners in New Zealand will understand that these moves are in the national interest, and will take these changes in their stride.
Cabinet agreed to overhaul the law when it met on Monday, 72 hours after the horrific terrorism act in Christchurch. Now, six days after this attack, we are announcing a ban on all military style semi-automatics (MSSA) and assault rifles in New Zealand.
"Related parts used to convert these guns into MSSAs are also being banned, along with all high-capacity magazines.
"An amnesty will be put in place for weapons to be handed in, and Cabinet has directed officials to develop a buyback scheme. Further details will be announced on the buyback in due course."
Police Association president Chris Cahill said the just-announced reforms represented "a fine balance" between the practical requirements of legitimate firearms users throughout the country, and the need to protect society.
"I hope that the moves immediately attract cross party support because it is important for New Zealanders to know that their political leaders are all on board with this extremely important move," he said.
"These are weapons that have been used to slaughter innocent children, women and men while they were at their most vulnerable – at prayer. It is a move we, as a community, can be proud of."
Cahill said while the changes were significant and bold, they were only the first steps.
The next steps needed to include a reconsideration of a firearms registry so it was known how many firearms were in the country, along with a review of the Arms Act.
"The act is dated and needs an overhaul sooner rather than later," Cahill said.
"Today we have the initial steps, but we should bear in mind that way back in 1997 the key recommendation of the Thorp report was for a full review of the act.
"We didn't do it then, but we can make up for that by conducting a full review in the very near future," Mr Cahill said.
"Today is an extraordinary day that was brought about by dreadful events. This Government has acted swiftly and is sending a message nationally and internationally that the types of weapons and equipment used to enhance the capacity of those weapons to kill many people are not welcome here."