The man due to go on trial for the 15 March 2019 Christchurch mosque attacks is reported to have today (Thursday) pleaded guilty to all the charges he was facing.

RNZ News reports that, at the High Court in Christchurch, Brenton Tarrant admitted 51 counts of murder, 40 of attempted murder and one under the Terrorism Suppression Act.

In previous pre-trial hearings he had denied all of the charges. The guilty plea means he has become New Zealand's first convicted terrorist.

In a statement, Prime Minister Jacinda Adern said the guilty plea will provide some relief to the many people whose lives were shattered by what happened on March 15.

“These guilty pleas and conviction bring accountability for what happened and also save the families who lost loved ones, those who were injured, and other witnesses, the ordeal of a trial," she has said.

Ms Adern said she could not make any further comment given that sentencing is still to happen.

Last week Chief High Court Judge Venning and Chief District Court Judge Taumaunu advised the New Zealand Law Society | Te Kāhui Ture o Aotearoa and New Zealand Bar Association of the arrangements being put in place for the R v Tarrant trial.

The arrangements would have had an impact on other cases in Christchurch.

The trial was set down to begin on 2 June, and was expected to take six weeks to complete.

RNZ News reports the 29-year-old showed no emotion as he appeared via audio visual link in the High Court.

They say no explanation for the Australian's change of heart was given during the hearing. He has been remanded in custody until May.

No sentencing date has been set as the courts continue to grapple with widespread disruption from the COVID-19 outbreak.