In the immediate aftermath of last Friday's shootings at two mosques in Christchurch, Ardern labeled the attack as terrorism and said New Zealand's gun laws would change.

"On 15 March our history changed forever. Now, our laws will too. We are announcing action today on behalf of all New Zealanders to strengthen our gun laws and make our country a safer place," Ardern told a news conference.

“All semi-automatic weapons used during the terrorist attack on Friday 15 March will be banned."

Ardern said she expects the new laws to be in place by April 11 and a buy-back scheme will be established for banned weapons.

The buyback would cost up to NZ$200 million ($138 million), she said.

All military data-style semi-automatics (MSSA) and assault rifles would be banned, along with parts used to convert weapons into MSSAs and all high-capacity magazines.

Under existing New Zealand gun laws, a standard A-category gun license allows semi-automatics limited to seven shots. Live-streamed video of a gunman in one of the mosques showed a semi-automatic weapon modified with a large magazine.

Australia banned semi-automatic weapons and launched a gun buy-back after the Port Arthur massacre in 1996 in which 35 people were gunned down.

Ardern said that similar to Australia, the new gun laws will allow for strictly enforced exemptions for farmers to conduct pest control and animal welfare.

"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."

New Zealand, a country of less than 5 million people, has an estimated 1.2-1.5 million firearms, around 13,500 of them MSSA type weapons.

Most farmers in the South Pacific country own guns, which they use for killing pests such as possums and rabbits, and for putting down injured stock. Recreational hunting of deer, pigs and goats is popular for sport and food, while gun clubs and shooting ranges dot the country.

That has created a powerful lobby which has thwarted previous attempts to tighten gun laws after other mass shootings in New Zealand and overseas.

REUTERS