New Zealand is to ban military-style semi-automatic rifles, with the government announcing a buyback just days after a shooting at two mosques killed 50 people.

The country will also ban assault rifles, high-capacity magazines, and certain modification parts, Prime Minister Jacinda Ardern said on Thursday.

“In short, every semi-automatic weapon used in the terrorist attack on Friday will be banned in this country,” she said.

“We are confident as a government that the vast majority of New Zealanders will support this change.”

An amnesty will allow the weapons to be handed in, with a buyback scheme to be announced soon, at an estimated cost of $NZ100 million to $NZ200 million ($96.8 million to $193.6 million).

Ms Ardern said the new laws would be in place by April 11.

In the meantime, the government has also implemented an immediate stop-gap measure to prevent the weapons from being sold and stockpiled, she said.

Ms Ardern said gun owners would have a reasonable time to ensure they met the new regulations.

“I have been steadfast in my belief that the vast majority of these owners will support what we are doing here today because it is about all of us,” she said.

“It is in the national interest and it is about safety.

“I will work hard to retain that support as we work on the remaining tranches of reform that we must make to prevent an act of terror happening in our country ever again.”

Next week, the New Zealand government will also consider tightening licensing rules and ammunition restrictions. A gun register is also being mulled.

Because there is no existing register, there is no figure for how many semi-automatic guns are in circulation in New Zealand. Last year, police estimated there were 14,000.

Dozens of New Zealanders, including some farmers who use the rifles for culling, have voluntarily handed in weapons to police since the attack.

Opposition Leader Simon Bridges said his party would back the changes.

An advertisement on the outskirts of Christchurch for a gun shop. Photo: Getty

After the Prime Minister’s announcement, Police Commissioner Mike Bush said the changes had immediate effect from 3pm on Thursday (NZ time).

“As a result of these changes many people who, up until now have owned these firearms legally, will no longer be able to possess them on their current licence conditions,” he said.

“This means for many people, you will now be in unlawful possession of your firearm.”

The amnesty would allow owners time to hand in their now-illegal guns, he said.

Concerns have been raised about the availability of military-style semi-automatic rifles in New Zealand after the accused gunman, 28-year-old Australian Brenton Tarrant, used two of the weapons, legally bought with a licence, in the shootings at two Christchurch mosques.

Thursday’s move came as New Zealand buried more of the 50 people who died in the attacks.

Fourteen-year-old Sayyad Ahmad Milne was buried on Thursday, a day after the funeral of his schoolmate Hamza Mustafa, 15.

There were six funerals on Wednesday and a further seven on Thursday morning, with more expected later in the day.

Preparations are also under way to reopen the mosques at the centre of the attacks for Friday prayers.

Al Noor Masjid, where 42 of last week’s 50 fatalities occurred, is expected to open in time.

Police also hope the community can return soon to the Linwood mosque.

Nationally, memorials are being planned at mosques around New Zealand on Friday to mark a week since the tragedy.

The Islamic call to prayer will be broadcast on television and radio across the country at the start of prayers on Friday. There will also be a two-minute silence to remember the dead.

In Christchurch, supporters of the affected mosques intend to gather and form a human wall of protection for people returning for the first time.

New Zealand Police will maintain a presence at both sites.

In total, 29 of the 50 people injured in the attack on March 15 remain in hospital. Eight are in critical condition.

Tarrant has been charged with one count of murder in relation to the shootings. He’s likely to face further charges when he returns to court next month.

-with AAP