The Christchurch terror attacks sparked an unmatched surge in white supremacist activity online, according to a US-based intelligence firm.

The director of the SITE Intelligence Group, Rita Katz, told The Sydney Morning Herald the online rallying behind the March 15 massacres had been unprecedented for right-wing attacks.

A total of 50 people were killed when a lone gunman opened fire on two Christchurch mosques.

It was the deadliest shootings in New Zealand's modern history.

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"Attacks always spark reactions from different extremist communities, but when it comes to the far right, there was never anything like the response to the Christchurch attack," Katz told The Sun-Herald.

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"His target, deadly execution, and his live-streaming of the event fuelled these communities' unprecedented response.

"The reactions were like nothing we've ever seen thus far from the far-right across the globe.

"If you compared it to jihadist attacks, it was like the 9-11 of far-right terrorists.

"Even the horrific Norway attacks by Anders Breivik didn't amass this level of universal approval by the far-right."

As a part of its monitoring, SITE had also noted calls to steal guns in a bid to circumvent newly cemented gun control law in New Zealand, according to The Sydney Morning Herald.

SITE had also discovered messaging from Muslim extremists that targeted Australians - one included use of Senator Fraser Anning's quote that pointed the finger towards Muslims as responsible for provoking the attacks.

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The Sydney Morning Herald reports that one message, shared on the day of the attacks, asked that supporters of the Islamic State "sharpen your knife" to attack Australians who were in Indonesia.