New Zealand will ban military-style semi-automatic and assault rifles under tough new gun laws following the killing of 50 people in a mass shooting on two mosques, Prime Minister Jacinda Ardern said on Thursday. In the immediate aftermath of last Fridays shootings in Christchurch, Ardern labelled the attack as terrorism and said New Zealands 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 new 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 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." Proponents of gun control in the United States and around the world praised the move and denounced the US pro-gun lobby on social media, while American gun supporters defended their constitutional right to bear arms.