"Every semi-automatic weapon used in the terror attack on Friday will be banned," Ardern said at a press conference in New Zealand capital Wellington on Thursday. "This legislation will be drafted and introduced in urgency."
Ardern said she hoped the law would be in place by April 11.
Ardern said that the "worst act of terrorism on our shores" had exposed a range of weaknesses in New Zealand's gun laws and promised that "Within 10 days of this horrific act of terrorism, we will have announced reforms that will, I believe, make our community safer."
"An amnesty will be put in place for weapons to be handed in, the cabinet has directed officials to develop a buyback scheme, "she said, adding that details on the buyback would be announced" in due course. "
"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," she said.
The Australian model
Police Minister Stuart Nash said the bill would include "narrow exemptions" for police and defense forces, as well as "legitimate business uses" such as professional pest control.
"Some guns serve legitimate purposes in our farming communities," he added, noting that exemptions had been made for 0.22 caliber rifles and shotguns used for duck hunting.
Immediate action would be taken to prevent people from stockpiling weapons before the change in law and encourage gun owners to surrender their weapons, he said.
In the wake of the reforms, mass shootings in Australia dropped to zero, gun suicides declined by an average of 4.8% per year, and gun-related homicides declined by an average of 5.5% per year.