New Zealand's government has further tightened the country's gun laws to establish a firearm register and overhaul licensing systems after 51 people were gunned down as they prayed at two mosques in Christchurch four months ago.

Monday's new legislation would tighten the rules for gun owners and dealers and require them to renew their licence every five years, Prime Minister Jacinda Ardern said. Currently, renewal takes place every 10 years.

"In April we acted to take the most dangerous weapons out of circulation by prohibiting assault rifles and military-style semi-automatics," Ardern said. 

"Now we are moving to stop other firearms falling into the wrong hands."

The register will link gun serial numbers with licence holders and give police more powers to intervene in cases where there are suspicions about a gun owner's behaviour. Visitors to New Zealand would also be prevented from buying a gun.

New Zealand banned military-style semi-automatic and assault rifles in the first phase of gun law reforms after Australian-born Brenton Tarrant used semi-automatic weapons to massacre Muslim worshippers in the city on New Zealand's south island.

He is alleged to have used five weapons, including two military-style semi-automatic rifles, in the killings.

He has pleaded not guilty to terrorism charges, as well as 51 counts of murder and 40 of attempted murder.

A gun buyback scheme, the first of some 250 collections to remove semi-automatic weapons from circulation, began earlier this month.

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