The Australian white supremacist who murdered 51 people at two New Zealand mosques in 2019 will appeal his conviction and life sentence, a court official told AFP Tuesday.

Armed with an arsenal of semi-automatic weapons, Brenton Tarrant attacked Friday worshippers at two mosques in March 2019, livestreaming the killings as he went.

His victims were all Muslim and included children, women and the elderly.

Tarrant pleaded guilty to 51 charges of murder and 40 counts of attempted murder, and was sentenced to life in prison without the possibility of parole -- the first time such a sentence was delivered in New Zealand.

"An appeal against convictions and sentence has been filed," Liz Kennedy, a spokeswoman in the Office of the Chief Justice, said Tuesday.

Last year, Tarrant's lawyer Tony Ellis said his client had believed "the simplest way out was to plead guilty", which amounted to a plea made under duress.

On Tuesday, Ellis told AFP he had been sacked and was unable to comment further on the case.

During sentencing in August 2020, Judge Cameron Mander said he was imposing the harshest possible term for Tarrant's "inhuman" actions.

"Your crimes are so wicked, that even if you are detained until you die it will not exhaust the requirements of punishment and denunciation," Mander said at the time.

After Tarrant's 17-minute livestream of his mosque attacks, Facebook said it removed a staggering 1.5 million videos that proliferated within the first 24 hours showing the harrowing viral footage.