WELLINGTON (Reuters) - New Zealand police expect tens of thousands of firearms to be surrendered in a guns buy-back scheme after parliament passed tough new firearm laws in the wake of the country’s worst peacetime mass shooting.

FILE PHOTO: Firearms and accessories are displayed at Gun City gunshop in Christchurch, New Zealand, March 19, 2019. REUTERS/Jorge Silva/File Photo

Lawmakers in New Zealand voted almost unanimously on Wednesday to change gun laws, less than a month after a lone gunman killed 50 people in attacks on two mosques in Christchurch.

The new legislation bars the circulation and use of most semi-automatic firearms, parts that convert firearms into semi-automatic firearms, magazines over a certain capacity, and some shotguns. This includes the gun used by the suspect in the Christchurch shooting.

It granted an amnesty until Sept. 30 for people to surrender prohibited items. More than 300 weapons had already been handed in, police minister Stuart Nash told parliament.

Police Deputy Police Commissioner Michael Clement told a news conference on Thursday that they are not sure how many guns they would receive as New Zealand has no law requiring people to register firearms.

“Its a great unknown question...everybody appreciates that there is no register of firearms with regards to the type of firearms we are talking about,” Clement said.

“So It could be in the tens of thousands, it could be more,” he added.

There are about 1.2-1.5 million firearms in New Zealand, according to gunpolicy.org. Of these, the government has said that a record of licenses show 13,500 firearms are military style semi-automatics (MSSAs). But the number could be higher.

Clement said details are being worked out of the gun buy-back scheme and he urged gun owners in possession of the prohibited firearms to register online.

Prime Minister Jacinda Ardern has estimated that the gun buy-backs would cost the government between NZ$100-200 million but other government ministers have warned that the costs could be higher depending on how many guns are handed to the police.

Authorities have charged Australian Brenton Tarrant, 28, a suspected white supremacist, with 50 counts of murder following the Christchurch attacks on March 15.