The imam of Al Noor Mosque believes the March 15 gunman didn't act alone and claims police failed to respond to suspicious behaviour days before the terror attack.

The Imam at Al Noor Masjid, Gamal Fouda, says a stranger was caught snooping around the Christchurch mosque a few weeks before the attack.

When the suspicious man was approached, he wouldn't give his name but claimed he wanted to know more about Islam.

The incident was so concerning to Fouda that images taken from mosque security cameras were handed over to police.

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But Fouda, who survived the March 15 massacre where 43 of his congregation were murdered during Friday prayer, says police didn't take the concerns seriously enough.

"The two weeks before the attack, lots of stories happened, which the police know about, and they are looking at," he told the Herald.

He also claims that around 2017, two white men arrived at the Deans Ave Masjid and abused people, claiming that they were not true Muslims like them.

They allegedly abused two worshippers and told them to go back to where they came from.

Fouda says he again raised his concerns with police.

Looking back, he now believes that they were white supremacists.

Photographs of the individuals were handed over to police, Fouda says.

Police have been approached for comment.

It all makes Fouda adamant the alleged gunman wasn't acting alone.

A 28-year-old Australian national has been charged with murdering 50 people. He is due back in court next month.

Christchurch businessman Philip Neville Arps - who owned a white supremacist themed insulation company – last month pleaded guilty to two charges of distributing footage of the Al Noor attack.

One charge was for sharing raw footage from the accused shooter's livestream to approximately 30 people on Facebook.

The other was for requesting the footage be modified by another person - having crosshairs and a "kill count" added.

The court heard he intended to distribute this modified footage as a meme.

A police statement says Arps, 44, said the modified footage was "awesome" - and says he showed no empathy for the people killed.

In 2016, Arps was one of a group of men who filmed themselves doing Hitler salutes as they delivered boxes of pigs heads and offal to the Al Noor Mosque.

"White power ... Bring on the cull," Arps was seen saying in the video.

High-tech security cameras powered by artificial intelligence gadgets that detect active shooters are being installed at Al Noor Masjid.

The state-of-the-art surveillance system is designed to detect an active shooter and alert police and other emergency services before shots are even fired.

The New Zealand mosque is understood to be the first place of worship in the world to be protected by the technology.