Isis has called on its followers to retaliate for the terror attack against Muslims in New Zealand last week, in a rare message from one of its top figures.

The group’s spokesman, Abu Hassan al-Muhajir, broke a six-month silence to call on Isis supporters to “take vengeance for their religion” in the 44-minute audio recording.

“This slaughter in those two mosques is no more than another tragedy among past and coming tragedies, which will be followed by scenes of force that reach all who were tricked to living among the polytheist,” he said in the message distributed by Al Furqan, a media organisation linked to Isis.

“The scenes of death in the two mosques are enough to wake the sleep and incite the supporters of the caliphate who live there, to take vengeance for their religion and for sons of their Ummah, who are killed everywhere in the world.”

The attack in Christchurch, New Zealand, left 50 people dead at two mosques during midday prayers. A 28-year-old Australian is the main suspect and in a manifesto, called himself a white nationalist out to avenge attacks in Europe by Muslims.

New Zealand shootings: Victims of Christchurch mosque terror attacks Show all 11 1 /11 New Zealand shootings: Victims of Christchurch mosque terror attacks New Zealand shootings: Victims of Christchurch mosque terror attacks Zakaria Bhuiyan People gather hoping to find out information about Zakaria Bhuiyan who is still missing after the mosques shootings in Christchurch. David Moir/AFP New Zealand shootings: Victims of Christchurch mosque terror attacks Mucad Ibrahim Three-year-old Mucad Ibrahim, the youngest known victim of the mass shooting at two mosques in Christchurch, New Zealand, on 15 March 2019. Abdi Ibrahim via AP New Zealand shootings: Victims of Christchurch mosque terror attacks Nadeem Rasheed Nadeem Rasheed, brother of Pakistani Naeem Rashid who died alongside his son Talha Naeem, 21, who were killed in shooting at a Mosque in Christchurch, at their home town in Abbottabad, EPA New Zealand shootings: Victims of Christchurch mosque terror attacks Omar Nabi Omar Nabi speaks to the media about losing his father Haji Daoud Nabi, 71, in the mosque attack REUTERS New Zealand shootings: Victims of Christchurch mosque terror attacks Ash Mohammed Ash Mohammed, right, talks to a police officer about his father and two brothers who are missing near the Masjid Al Noor mosque AP New Zealand shootings: Victims of Christchurch mosque terror attacks Akhtar Khokhur Akhtar Khokhur, 58, shows a picture of her missing husband Mehaboobbhai Khokhar, 65. AP New Zealand shootings: Victims of Christchurch mosque terror attacks Wasseim Alsati A note is seen on a window of a door at the family home of Wasseim Alsati in Christchurch on 17 March 2019. AFP/Getty Images New Zealand shootings: Victims of Christchurch mosque terror attacks Haroon Mahmood Relatives offer condolences to nephew (centre) of Haroon Mahmood, a Pakistani citizen who was killed in Christchurch mosque shootings. AP New Zealand shootings: Victims of Christchurch mosque terror attacks Farid Ahmed Farid Ahmed (pictured) survived the Al Noor mosque shootings but his wife Husne was killed. AFP/Getty Images New Zealand shootings: Victims of Christchurch mosque terror attacks Syed Areeb Ahmed A relative shows a picture of Syed Areeb Ahmed, a Pakistani citizen who was killed the Christchurch mosque shooting. AP New Zealand shootings: Victims of Christchurch mosque terror attacks Naeem Rashid A relative looks at a picture on a mobile phone of Pakistani nationals Naeem Rashid and his son Talha Naeem (right) who died in the Christchurch shootings. AFP/Getty Images

Isis has consistently made the argument to its followers that Muslims and non-Muslims cannot live side-by-side, and has used terror attacks such as these in its propaganda to make the case for its warped version of an Islamic state.

Even before the audio message appeared on Isis channels on the encrypted messaging app Telegram, experts had warned that the Christchurch massacre could be used for “reciprocal radicalisation”.

Isis supporters have claimed to avenge Muslims killed in Syria and Iraq, while far-right terrorists including the Finsbury Park attacker and the alleged New Zealand mosque shooter have claimed the same for victims of Isis-inspired attacks.

Security services fear a “domino effect” in atrocities and will be bracing for any potential impact from Isis’s latest call.

The message comes as the Isis caliphate, which once stretched for tens of thousands of miles and ruled over some 10 million people, is on the brink of defeat.

US-backed Syrian forces said they were close to capturing the last territory under Isis control on Tuesday, after taking most of a tent city where the group has made its last stand.

Although scattered clashes were continuing, a spokesman for the Syrian Democratic Forces said the battle would end “very soon”.

“This is not a victory announcement, but a significant progress in the fight against Daesh,” said Mustafa Bali, the SDF spokesman, on Twitter.

“The battles are not yet over. There are still some pockets next to the river. Some of the terrorists have taken their children as human shields. There are intermittent clashes,” Mr Bali said.

The battle to capture the last piece of the once mighty caliphate has gone on longer than anyone expected. Cornered in the small village of Baghouz, in Syria’s Deir ez-Zor province, the group’s most experienced fighters have put up a fierce fight.

An exodus of people has filed out of the village over the past two months, surprising Syrian and US officials. Some 60,000 people have fled the group’s dwindling enclave, nearly half of whom were surrendering supporters of Isis, including some 5,000 fighters.

But even on the brink of defeat, the group has continued its propaganda effort. Muhajir, who real name is not known, commented on the battle for Baghouz on Tuesday.

“Do you think the displacement of the weak and poor out of Baghouz will weaken the Islamic State? No,” he said.

Isis’s defeat at Baghouz will end its control of inhabited land in the third of Syria and Iraq that it captured in 2014. However, the group will remain a threat, regional and western officials say