The Australian gunman who killed dozens of people during attacks on two mosques in New Zealand has been sentenced to life in prison without the possibility of parole.

Brenton Harrison Tarrant had pleaded guilty during court proceedings in Christchurch to murder, attempted murder and terrorism over the attacks in the city which left 51 people dead.

Tarrant had the opportunity to speak on the final day of a four-day hearing which had seen 90 survivors and family members talk about the pain of the March 2019 attacks at two mosques in the city.

The killer had earlier sacked his legal team but was appointed a standby lawyer at the high court in Christchurch.

Tarrant confirmed to Justice Mander that he did not wish to speak during the sentencing hearing.

Many of the victims and family members who spoke at the hearing asked the judge to impose the maximum possible penalty - life without the possibility of parole.

The Australian showed little emotion during the sentencing. He has watched the speakers, occasionally giving a small nod or smirking at jokes made at his expense.

The attacks targeting people praying at the Al Noor and Linwood mosques shocked New Zealand and prompted new laws banning the deadliest types of semi-automatic weapons.

They also prompted global changes to social media protocols after the gunman livestreamed his attack on Facebook, where it was viewed by hundreds of thousands of people.