The Australian man who carried out the Christchurch massacre has been charged with 50 counts of murder and 39 counts of attempted murder.

Key points: The fresh charges against Tarrant were released in a written statement by New Zealand Police

The fresh charges against Tarrant were released in a written statement by New Zealand Police Police said other charges were still under consideration

Police said other charges were still under consideration His case will be heard in the Christchurch High Court on April 5

New Zealand Police announced the fresh charges against Brenton Harrison Tarrant, 28, in a written statement on Thursday afternoon.

Tarrant was arrested on March 15 for his involvement in the shooting deaths of 50 people at two mosques in Christchurch and charged with one count of murder, but police indicated further charges would be laid.

Police said other charges were still under consideration.

The former personal trainer stormed two mosques in Christchurch with a number of high-powered weapons and live streamed the attack online, in what is alleged to be the single-worst terrorist attack carried out by an Australian.

Tarrant's case will be heard in the Christchurch High Court on Friday. He will appear via video link from the maximum security prison in Auckland where he is in custody.

The judge presiding over the case said the hearing will mainly be about Tarrant's legal representation. Tarrant has said he wants to represent himself, and he will not be required to enter a plea.

"The principal purpose of the call on April 5 will be to ascertain the defendant's position regarding legal representation and to receive information from the Crown regarding certain procedural steps and when it is envisaged those steps will be completed," Judge Cameron Mander said in court minutes.

Tarrant live-streamed the March 15 attack online and posted a rambling "manifesto" describing his motivations.

He worked as a personal trainer at a gym in Grafton after he finished school, before travelling overseas to Asia and Europe.

At a March 16 court appearance, Tarrant did not apply for bail or for the suppression of his name and made a white power gesture as he was brought into the court.

New Zealand Prime Minister Jacinda Ardern has flagged changing the country's gun laws amid revelations Tarrant had a gun licence that allowed him to legally obtain weapons.

Ms Ardern has said security officers would be stationed at mosques throughout New Zealand in the foreseeable future.