New Zealand Prime Minister Jacinda Ardern says reforms to the country's gun laws will be announced within 10 days following the shootings at two Christchurch mosques that left 50 people dead and dozens injured last week.

She said cabinet ministers had met and made an in-principle decision to tighten gun ownership laws, but details still need to be worked out.

Ardern also announced an inquiry into the events leading up to the shootings and whether there was anything the country's intelligence services could have done to prevent them.

Brenton Harrison Tarrant, the 28-year-old Australian white supremacist charged in the massacre, wasn't on authorities' radar before his well-planned attack on two mosques, and there have been concerns that intelligence agencies were overly focused on the Muslim community when it came to detecting and preventing security risks.

People visit a memorial site for victims of last Friday's shooting in front of Al-Noor Mosque in Christchurch on Monday. (Jorge Silva/Reuters)

At a news conference, David Tipple, the owner of Gun City, a Christchurch gun store, said the store sold four guns and ammunition to Tarrant through a "police-verified online mail order process." The store "detected nothing extraordinary" about the buyer, he said.

Police Commissioner Mike Bush said police are certain that Tarrant was the only gunman but aren't ruling out that he had support.

Watch: Far-right extremism and the New Zealand attacks:

The deadly mosque shootings in Christchurch have put the spotlight on far-right extremism and the influence of white supremacy. 9:35

"I would like to state that we believe absolutely there was only one attacker responsible for this," he said at a news conference.

"That doesn't mean there weren't possibly other people in support, and that continues to form a very, very important part of our investigation."

None of the guns sold to Tarrant were military-style, semi-automatic weapons, according to Tipple. It was not clear if any of the firearms Tarrant purchased from Gun City were used in the shootings.

People gather outside the Al-Noor Mosque, where 42 people were gunned down. (Jorge Silva/Reuters)

In vowing to tighten gun laws, Ardern has said the attacker used five guns, two of them semi-automatic, which were purchased with an ordinary gun licence and modified.

Tipple said he was disgusted by the killings but felt no responsibility for the tragedy and refused to say whether he believed gun ownership laws should change in New Zealand, insisting that a debate over guns should be held at another time.

His store has been criticized in the wake of the shootings for leaving out a roadside advertising billboard that shows a parent helping children with rifle target practice.

Canada mulls reforms

In Canada, Public Safety Minister Ralph Goodale suggested the deadly mass shooting in New Zealand will spur parliamentarians to take a careful look at Canada's own gun laws.

Public Safety and Emergency Preparedness Minister Ralph Goodale said on Monday that the tragedy in Christchurch would prompt Canada to reconsider its own gun laws. (Adrian Wyld/Canadian Press)

Goodale said the killing of 50 people in Christchurch has sparked a global sense of concern that will prompt Canadian politicians to make some timely decisions.

In the House of Commons on Monday, party leaders expressed solidarity with the victims in Christchurch and their families.

A visibly angry Prime Minister Justin Trudeau denounced the "small, toxic segments" of society that peddle the belief diversity is a weakness, spewing hatred and inciting brutality.

Watch: Trudeau's full statement on New Zealand attack

Prime Minister Justin Trudeau's full statement in the House of Commons on the terror attack in New Zealand. 18:06

Conservative Andrew Scheer joined Trudeau in stressing the need to condemn all racist ideologies and doctrines of prejudice while the NDP's Jagmeet Singh said the use of dehumanizing language and making immigration out to be a threat could breed fear and fuel hatred.

Goodale said his cabinet colleague Bill Blair will deliver recommendations soon after having been asked last August to study a full ban on handguns and assault weapons in Canada.

A bill already before Senate would, among other things, expand the scope of background checks on those who want to acquire guns here.

Instead of just the five years immediately preceding a licence application, questions about buyers' histories would cover their entire lifetimes.

The bill would also require gun retailers keep records of firearms inventory and sales and ensure the purchaser of a hunting rifle or shotgun presents a firearms licence that the seller would have to verify.