The gunman described his actions as a "terrorist act" and his social media accounts were blocked after he published an extremist manifesto and live-streamed the shooting on Facebook.

Social media platforms Twitter, Instagram and Facebook have suspended the accounts of the man suspected of being behind the recent shooting rampage at mosques in New Zealand.

The man live-streamed himself gunning down dozens of worshippers at the Al Noor Mosque in the centre of Christchurch on Friday. He killed 41 people at that mosque, 7 at another one, and a 49th victim died in hospital.

New Zealand police were aware of the footage doing the rounds on social media and asked users not to circulate it. "It shouldn't be in the public domain and we are doing everything we can to remove it," police chief Mike Bush told reporters.

Mia Garlick, a spokeswoman for Facebook New Zealand, said the company pulled videos of the Christchurch shootings following a police request.

"New Zealand Police alerted us to a video on Facebook shortly after the livestream commenced and we quickly removed both the shooter's Facebook and Instagram accounts and the video," she said.

The shooter was identified as a 28-year-old Australian; in the video, he called himself Brenton Tarrant. He published his manifesto before the attack, wherein he described himself as a "fascist" and said he was disappointed by immigrants, who have higher fertility rates and "replace" Europeans.

Police have arrested four suspects in connection with the attacks; one man was indictedon murder charges and will appear in court tomorrow; one person was deemed innocent while two others are still being investigated.