Jacinda Ardern has confirmed New Zealand will toughen its gun laws after 50 people were murdered in a terror attack at two mosques in Christchurch.

Ms Ardern has encouraged New Zealanders to surrender their semi-automatic weapons through a voluntary amnesty, as her government works through changes to firearm laws over the next week.

“To make our community safer, the time to act is now,” she said on Monday.

New Zealand’s cabinet has agreed in-principle to a range of gun reforms, but Ms Ardern would not be drawn on the detail.

The proposed changes will be announced before cabinet meets again next week.

Semi-automatic assault rifles are expected to be banned in New Zealand, and gun owners are likely to face much more stringent registration requirements.

“There are details to work through,” Ms Ardern said.

“These aren’t simple areas of law, so that’s simply what we’ll be taking the time to get right.”

Deputy Prime Minister Winston Peters endorsed the plan.

“At 1pm on the 15th of March our world changed forever, and so will our gun laws,” Mr Peters said.

-AAP