The main suspect of killing 49 people in shootings at two mosques in New Zealand on Friday has appeared in court on a single murder charge.
Australian Brenton Tarrant, 28, was brought to the dock in a white prison shirt and handcuffs. Further charges are expected to be made against him.
PM Jacinda Ardern said Mr Tarrant had five guns and a firearms licence, adding: "Our gun laws will change."
Two others are in custody. None of those detained had a criminal record.
Mr Tarrant, who stood silently during the brief hearing, was remanded in custody without plea and is due appear in court again on 5 April.
Ms Ardern called the attack "an act of terror".
The first person to be publicly identified has been named as 71-year-old Daoud Nabi, originally from Afghanistan.
PM: He wanted to continue the attack
Ms Ardern, who had earlier described the shooting as a "terrorist attack", said the guns used by the attacker appeared to have been modified, and that the suspect's car was full of weapons, suggesting "his intention to continue with his attack".
Speaking at a news conference on Saturday, she said the suspect had obtained a gun licence in November 2017 that allowed him to buy the weapons used in the attack.
"The mere fact... that this individual had acquired a gun licence and acquired weapons of that range, then obviously I think people will be seeking change, and I'm committing to that."
New Zealand's Attorney-General David Parker said the government would look into banning semi-automatic weapons, but that no final decision had been made.
'A rejection of hate'
Rupert Wingfield-Hayes, BBC News, Christchurch
All day on Saturday the people of Christchurch have been turning out to show their rejection of the hate that inspired Friday's horrific attacks.
In ones and twos and in family groups, people have been coming by the hundred to a makeshift memorial set up on the edge of Hagley Park. Outside the two mosques that were attacked, people have been laying more flowers. Many have left hand-written notes. "This is not New Zealand," one read.
At one point a group of young men started quietly singing a traditional Maori song, their heads bowed, eyes closed. The mayor of Christchurch said the killer had come to the city with hate in his heart, to perform an act of terrorism. But she said he did not represent anything about the city.
Still, there are lots of uncomfortable questions for the authorities here. The man now in custody, Brenton Tarrant, made no secret of his support for white supremacy. He had reportedly been planning the attacks for months. And yet he was not on any police watch list. He did not have any trouble getting a gun licence nor in buying a collection of high-powered weapons.
On Saturday, New Zealand Prime Minister Jacinda Ardern said attempts had been made repeatedly to tighten New Zealand's gun laws, but all had failed. After Friday's terrible attack, she said, it must now happen.
Suspect 'not on radar'
The suspect had "travelled around the world with sporadic periods of time spent in New Zealand", Prime Minister Ardern said, without formally identifying him.
Ms Ardern said New Zealand intelligence services had been stepping up investigations into far-right extremists, but added: "The individual charged with murder had not come to the attention of the intelligence community nor the police for extremism."
Before the attacks, social media accounts in the name of Brenton Tarrant were used to post a lengthy, racist document in which the author identified the mosques that were later attacked.
The text is called "The Great Replacement", a phrase that originated in France and has become a rallying cry for European anti-immigration extremists. The suspect said he had began planning an attack after visiting Europe in 2017 and being angered by events there.
What are New Zealand's gun laws?
- The minimum legal age to own a gun in New Zealand is 16, or 18 for military-style semi-automatic weapons
- All gun owners must have a licence, but most individual weapons do not have to be registered - New Zealand is one of the few countries where this is the case
- Applicants for a firearm licence must pass a background check of criminal and medical records, including factors such as mental health and domestic violence
- Once a licence has been issued, gun owners can buy as many weapons as they want
First victim named
Daoud Nabi moved to New Zealand in the 1980s, and described the country as "a slice of paradise", his son Omar told AFP news agency.
The identities of the other victims have not yet been released.
Prime Minister Ardern also spoke about the importance of reuniting relatives with their loved ones "as quickly as possible", and said that bodies were still being removed from the Al Noor mosque, the site of the first attack.
Financial support would be made available to those who had lost someone on whom they were financially dependent, she added.
A total of 48 people were wounded in the shootings. Among those injured are two boys aged two and 13. Eleven of those being treated at Christchurch Hospital are in a critical condition in intensive care, chief of surgery Greg Robertson said.
Bangladesh, India and Indonesia all say some of their citizens were killed in the shooting and others are unaccounted for.
Christchurch Mayor Lianne Dalziel expressed "revulsion" at this "act of terrorism" and voiced solidarity with the victims. "We have welcomed new people into our city. They are our friends, they are our neighbours."
She added that flags would fly at half-mast on government buildings in the city "until further notice".
Security remains tight across Christchurch. All mosques in New Zealand have been closed.
How events unfolded
The first report of an attack came from the Al Noor mosque in central Christchurch during Friday prayers at 13:40 (00:40 GMT).
A gunman drove to the front door, entered and fired on worshippers for about five minutes.
The gunman, who live-streamed the attack from a head-mounted camera, identified himself in the footage, which showed him shooting at men, women and children.
The gunman is then said to have driven about 5km (three miles) to another mosque in the suburb of Linwood where the second shooting occurred.
Police say they recovered firearms from both mosques, and explosive devices were found in a car belonging to one of the suspects.
According to the latest census figures, Muslims make up about 1.1% of New Zealand's population of 4.25 million. Numbers rose sharply as New Zealand took in refugees from various war-torn countries since the 1990s.