Christchurch terror attack: Islamic State, 'every major jihadist group' call for retaliation

Islamic State (IS) and "every [other] major jihadist group" are calling for retaliatory attacks in the wake of a shooting targeted at Muslims in Christchurch last week.

On Friday, there were shootings at two mosques in Christchurch - an appalling act of violent terrorism that claimed 50 lives.

In response, IS's official spokesperson has broken a lengthy silence to issue a 45-minute-long audio recording promising vengeance.

"[The recording] was released via an app," Rukmini Callimachi, the New York Times journalist who broke the story, explained to Radio New Zealand on Wednesday.

"Ironically, it is the same app that is being used by white extremists to pass around the video of the Christchurch attack."

Callimachi, who has reported extensively on IS, told the station the spokesperson - a mysterious figure who goes by the pseudonym Abu Hassan al-Muhajir - began his lengthy speech with a call to arms.

"This is his first statement in six months and at the very top of it he called for retaliation against the killing of Muslims in the two mosques in New Zealand," she said.

"There seems to be a unifying rallying cry amongst the jihadist organisation that sees this as a crime against their religion and want to pay it back in blood."

The journalist says IS is one of many Islamic extremist organisations calling for vengeance.

"ISIS is not the only jihadist group that is calling for retaliatory attacks in relationship to what has happened Christchurch. So far, almost every major jihadist group has called for that."

Callimachi says the threat of retaliation is believed to be authentic, as IS rarely makes false statements. However, the group is far less powerful and influential now than it has been in previous years.

In February, it was reported that IS had been reduced to one tiny enclave on the Euphrates, and was on the brink of total defeat.