New Zealand's police chief said today the police were working with global intelligence agencies to build a profile of the shooter who killed 50 people at mosques in Christchurch last week.

"I can assure you this is an international investigation," Police Commissioner Mike Bush (photo, above) said at a media briefing in the capital Wellington. New Zealand Prime Minister Jacinda Ardern has said the suspect in the shooting had travelled around the world and was not a long-term resident.

Bush said the probe involved New Zealand police, the local intelligence community and partners around the world, including officials from the US Federal Bureau of Investigation (FBI) who were in the country and police and intelligence officials from Australia.

"We are also working very closely with other Five Eyes partners in terms of cooperation around the profile, travels, etc, to build a comprehensive picture of this person that we will put before the court," Bush said.

New Zealand is part of the Five Eyes intelligence network that includes the United States, Australia, Canada and Britain.

Australian Brenton Tarrant (photo, below), 28, a suspected white supremacist who was living in Dunedin, on New Zealand's South Island, has been charged with murder. He was remanded without a plea and is due back in court on April 5, when police said he was likely to face more charges.

Giving details on the timeline of last Friday's attack, the police chief said first responders arrived within five minutes and 39 seconds of being informed of the incident and the shooter was caught within the building.

"We strongly believed the person was on his way for a further attack," he said.

After days of mourning, preparations for the first burials were gathering pace in Christchurch today, amid frustration among family members who have complained about delays in handing over the bodies.

Burials are expected to start today in Christchurch.

Commissioner Bush said as of last night, 21 of the victims had been formally identified. They were ready to be reunited with their families, he said, adding some have been handed to the families.

The majority of the identifications would be completed by tonight, he added. About 120 people were involved in the process, including dozens of pathologists and forensic experts.

Speaking of the delays, Bush said the police had to prove the cause of death to the satisfaction of the coroner and the judge handling the case.

"You cannot convict for murder without that cause of death. So this is a very comprehensive process that must be completed to the highest standard," he said.

Tragedy for a school

Ardern (photo, below) visited the Cashmere High School in Christchurch, whose students and parent community were among those most impacted by the attacks.

Two boys from the school - teenagers Sayyad Milne and Hamza Mustafa - were killed in the attacks. One former student, Tariq Omar, was also killed, while Khaled Mustafa, the father of Hamza, also died.

Another student, as well as two other fathers, are still being treated for gunshot wounds at the hospital.

About 200 children gathered at the school auditorium and listened to Ardern, who spoke to them about racism and changes in gun laws. She said: "Never mention the perpetrator's name… never remember him for what he did."

The students performed an emotionally-charged haka, a ceremonial war dance, for Ardern.

As she was leaving, a little girl ran up to Ardern and hugged her. The prime minister hugged her back.

"The impact of this terror attack has been particularly cruel and tough for our school community," the school principal Mark Wilson said in a statement last night.

- Reuters