The first of more than 250 collections to be held nationwide was held in Christchurch where 51 Muslim worshippers were gunned down while at prayer less than four months ago.

The government, with support from opposition parties, immediately rushed through legislation to tighten New Zealand's gun laws.

Police Minister Stuart Nash said the one objective was to "remove the most dangerous weapons from circulation".

With armed police monitoring the handover, 68 firearms owners handed in 97 weapons and 94 parts and accessories in the first two hours.

The regional police commander Mike Johnson said 903 gun owners in the Canterbury area had registered 1,415 firearms to be handed in.

"Police recognise that this is a big change for the law-abiding firearms community and we are hearing really positive feedback from people as they come through today that they are finding the process works well for them," Johnson said.

Ray Berard, who moved to New Zealand from Canada 25 years ago, handed in an assault rifle and told reporters he had been in the Canadian army and on the Canada shooting team but believed there was no place for military-style firearms in modern society.

"My wife is working as one of the project directors on the hospital rebuild and we were there on the day of the shooting and watched the 35-odd hearses leave the next day," he said.

A person can "do a lot of damage to a lot of people... if you're mentally unwell and you have a weapon that can shoot 100 rounds a minute."

Australian-born Brenton Tarrant has been charged with the killings and is alleged to have used an arsenal of five weapons, including two military-style semi-automatic rifles (MSSAs), in the attacks on two mosques.

He has pleaded not guilty to terrorism charges, as well as 51 counts of murder and 40 of attempted murder.