A white supremacist gunman who killed 51 people in New Zealand failed to appear in court on Thursday as he sought judicial review of his prison conditions and his designation as a terrorist.

Australian national Brenton Tarrant is serving a life sentence without parole for the murders at two Christchurch mosques in March 2019, the worst mass shooting in the country's history, an act he livestreamed online.

Tarrant was expected to represent himself at the High Court hearing by joining via video-link from an Auckland jail, during which he was supposed to challenge his designation as a "terrorist entity" under the Terrorism Suppression Act.

He pleaded guilty to terror offenses at his original trial in 2020.

But the 30-year-old failed to appear and judges adjourned proceedings until a later date.

They gave no details as to the reasons for Tarrant's no-show, but it is expected to have no bearing on his legal challenge.

What is the background to the case?

Tarrant became the first person in New Zealand's history to be given a life sentence without parole after he admitted to the murders.

He was also convicted of the attempted murder of another 40 people and one charge of terrorism.

On sentencing Tarrant last August, Judge Cameron Mander said: "Your crimes are so wicked that even if you are detained until you die, it will not exhaust the requirements of punishment."

In New Zealand and other common law countries, a sentence without parole means the offender will not be given the opportunity to leave prison after serving only a portion of their sentence.

Tarrant moved to New Zealand in 2017 when he started planning his attacks on the country's Muslim community.

Shortly before the killings, he posted a 74-page white supremacist manifesto online.

jf/msh (dpa, Reuters)