The Office of Film & Literature Classification has said it banned the Christchurch terrorist attack livestream because it was "clearly intended to record, share and glorify the acts of extreme violence and cruelty".
Chief Censor David Shanks officially banned the 16-minute and 55-second video last week, labelling it as "objectionable".
"The video promotes and supports the infliction of extreme violence and cruelty," the decision summary said.
"The video is clearly intended to record, share and glorify the acts of extreme violence and cruelty, namely the graphic mass murder of unsuspecting victims who are powerless to resist," he said.
Fifty people were killed and 50 others were injured at the attacks on Al Noor Mosque and the Linwood Islamic Centre on March 15.
Captured in "first person", the video was filmed from a helmet-mounted camera and was livestreamed on Facebook.
In the Classification Criteria section of the Office's decision, it explained the video deals with matters of "horror, crime, cruelty and violence".
"It documents events immediately prior to, during, and after the mass murder of peaceful and unarmed civilians at a Christchurch mosque," it reads.
The publication reportedly written by the alleged gunman had also been classified as objectionable by the Chief Censor.
That means it is an offence to distribute or possess that document.
In the days since the attack, police have arrested several people who shared the disturbing footage of the attack at Al Noor Mosque on Deans Ave.
Police, the Courts and other enforcement agencies are permitted to possess the video due to forensic and evidentiary value.
Anyone who sees the material or video online was asked to report it immediately.
According to the Department of Internal Affairs, those who "knowingly" have possession of or share the objectionable material carries a jail term up to 14 years.
Fines of up to $10,000 may also be imposed on those convicted of the offence.