"In respect for the victims of the Christchurch terror attacks and because the elevated security risks we have decided to not hold the event," the Kumeu Militaria show said in a Facebook post.

A gunman killed 50 people and wounded another 50 after opening fire on two Christchurch mosques during prayers last Friday.

Australian white supremacist Brenton Tarrant - who has been charged with murder in relation to the attacks - obtained a NZ gun licence in November 2017 allowing him to buy the weapons, including two semi-automatic rifles, beginning the following month.

The weapons are understood have to have been illegally modified and the issue, along with the availability of semi-automatics are now being swiftly reviewed.

The shootings have prompted Prime Minister Jacinda Ardern to promise changes to the relatively relaxed gun laws in New Zealand.

Changes to the laws have previously been rejected, but Ms Ardern is determined to make it happen.

"We cannot be deterred from the work we need to do on our gun laws in New Zealand," she said on Sunday.

"They need to change, regardless of what activity may or may not have happened with gun retailers."

Cabinet will start preliminary discussions on gun laws on Monday.

There are an estimated 1.5 million firearms in New Zealand - roughly one for every three citizens.

The gun show was to be held in Auckland this Saturday.

The Kumeu Militaria Facebook page says the show is an event with the aim of "supporting those that serve our country and promoting an interest in our military history".

Australian Associated Press