New Zealand will establish a team of investigators dedicated solely to tackling online extremism, as it moves to address failures exposed by the Christchurch mosques massacre, Prime Minister Jacinda Ardern said on Monday.

Ardern has led global efforts to force technology firms to clamp down on extremist material since a lone gunman killed 51 Muslim worshippers in March, streaming part of the atrocity on Facebook.

But she said the attack, which targeted two mosques in the South Island city, also showed her own government needed to improve resources to curb the spread of online hate.

“We will have a dedicated team focused on targeting and disrupting violent extremist content across our digital channels,” she said.

“This will work in a similar way to how we target child sexual exploitation material, by working with online content hosts to find and remove harmful content.”

Ardern said the Internal Affairs department would hire 17 specialists in investigative, forensic and intelligence work to focus on violent extremist content online.

Within 24 hours of the Christchurch attack, allegedly carried out by a self-described white supremacist, Facebook had removed 1.5 million posts of the video streamed by the alleged killer.

New Zealand Internal Affairs Minister Tracey Martin said response times from authorities needed to be better so objectionable material was removed more quickly, denying extremists a platform.

“The ease and speed with which the March 15 terrorist attack spread online showed we need to improve our systems to respond just as swiftly,” she said.

Ardern said the latest move complements her push to make global tech giants more accountable for online extremism and more responsive to requests to remove it, which she has called the Christchurch Call.

Companies such as Facebook, Amazon, Google, Twitter and Microsoft have all signed up to the initiative.

Ardern has also tightened New Zealand's gun laws in the wake of the massacre and set up a judicial review into whether police and intelligence services missed warning signs about the threat posed by right-wing extremists.

The alleged Christchurch gunman, Brenton Tarrant, has pleaded not guilty to 51 counts of murder, 40 of attempted murder, and engaging in a terrorist act.

His trial will begin on June 2 next year in Christchurch.