New Zealand mosque shootings: Brenton Tarrant admits carrying out deadly attacks in Christchurch

A white supremacist accused of killing 51 Muslim worshippers in New Zealand's worst mass shooting has changed his plea to guilty.

Brenton Tarrant, appearing in court by video link on Thursday, admitted to 51 charges of murder, 40 charges of attempted murder and one charge of committing a terrorist act.

The in a hastily-called hearing at Christchurch High Court was arranged as the country went into lockdown due to the coronavirus pandemic that has swept across the world.

"He has been convicted of each and every one of those charges," presiding judge Justice Cameron Mander said in minutes of the hearing released by the court.

"The entry of guilty pleas represents a very significant step towards bringing finality to this criminal proceeding."

Tarrant has been in police custody since March 15, 2019, when he was arrested and accused of using semi-automatic weapons to target Muslims attending Friday prayers at two mosques in Christchurch.

The attack was streamed live on Facebook.

The 29-year-old Australian man's guilty plea makes a six-week trial that was due to begin in June redundant.

The court will instead move directly to sentencing Tarrant on all 92 charges. It did not provide a date for that sentencing and Tarrant was remanded in custody until May 1.

Prime Minister Jacinda Ardern, who has stuck by a pledge to not name the gunman in public, said she let out "a massive sigh of relief" when she heard of the guilty pleas.

"The whole nation, but particularly the Muslim community, has been spared a trial that could have acted as a platform," the PM said.

Aarif Rasheed, a lawyer working with some victim families, said they were not given any indication of why Tarrant changed his pleas from not guilty.

"Any possible explanations are speculative but we do know terrorists are often seeking a sense of self-importance and attention to their cause," Rasheed said. "The COVID-19 pandemic has removed that."

Tarrant, who faces a lifetime prison sentence, had posted a "manifesto" on social media ahead of the attack that called immigrants "invaders" and referred to "white genocide", a term used by white supremacists to describe the growth of minority populations.

Due to a nationwide lockdown in place for the coronavirus outbreak, Thursday's court hearing took place with just 17 people in the courtroom, including an Imam for each of the two mosques attacked.

Sheikh Hasan Rubel, 35, who survived from the attack despite being shot three times, said the guilty pleas brought both surprise and relief.

"Whenever I thought about the court proceedings it used to affect me mentally, and I did not want to re-live all of it," he told Reuters over the phone.

"Now I feel quite relieved. We had faith in New Zealand's legal system and I was sure he will get whatever he deserves."

Farid Ahmed, whose wife was killed at the Al Noor mosque, said the guilty plea was the courageous and right thing to do.

"His heart has realised what is right and he has admitted his guilt," Farid said.

"That would save him from more emotional and mental trauma, and the rest of country's time and efforts," he added. "For Muslim community, it wold save them from going through the court process and refreshing memories of this tragedy."