New Zealand Prime Minister Jacinda Ardern announced Thursday strict new gun laws in the wake of last week's terror attack on two mosques in Christchurch that killed 50 people.

Speaking at a press conference in the capital Wellington, Ardern said all military-style semi-automatic weapons, assault rifles and high-capacity magazines will be banned.

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

(Prime Minister Jacinda Ardern speaks to media during a press conference at Parliament on March 21, 2019 in Wellington.)[Getty/Kyodo]

In last Friday's attack in Christchurch, a lone gunman opened fire on two mosques during midday prayers, killing 50 and injuring a further 50.

The shocking incident is New Zealand's greatest peace-time mass shooting and has exposed what Ardern described as a number of weaknesses and loopholes in the country's gun laws.

Australian-born Brenton Tarrant, the alleged gunman, is understood to have primarily used two guns, both assault rifles, which he purchased legally on a "category-A" license, the standard category of gun license available to anyone in New Zealand over the age of 16 who meets police checks.

The prime minister explained that the guns were modified to use high-capacity magazines, "essentially turning them into military-style semi-automatic weapons."

"While the modification (of the weapons) was illegal, it was done easily through a simple online purchase," she said.

The government's proposal will be taken to parliament for debate, but Ardern said she expects the law to be passed by April 11.

Soon after the announcement, the leader of New Zealand's opposition party released a statement saying it supports the proposed changes.

The announcement also received public support from organizations that regularly use firearms such as Fish and Game New Zealand and Federated Farmers.

In Hagley Park, opposite the Al Noor Mosque where 42 people were shot dead, Faheem, 37, who travelled to Christchurch from Auckland to support the local Muslim community, said it was for the good of the entire nation that the gun laws change.

"People can feel relieved that the guns are not that available anymore," he said.

However, a 43-year-old woman, Lisa, who only gave her first name, said she was less sure about whether the change in gun laws was the correct move from the government.

"I genuinely don't know if it's necessary or if this is just a reaction," she said.

The prime minister, who has been internationally lauded for her swift but empathetic response to the terror attack, said interim measures were put into place at the time of her announcement to ensure that all weapons flagged to be banned would require extra police endorsement in order to be purchased, effectively preventing all further sales.

A gun buy-back system will also be introduced to ensure that individuals who previously bought the weapons legally will be compensated for surrendering their firearms once the ban comes into effect.

It is estimated that the buyback will cost the government NZ$100 million to NZ$200 million (around $69 million to $138 million).

Because New Zealand does not require individual firearms to be registered, the exact number of guns in New Zealand is unknown. As a result, the government can only estimate the total cost.

Almost 240,000 people -- or roughly 6 percent of New Zealand's voting population -- hold a firearm license. It is estimated there are 1.5 million guns currently in the country.