Two of the purported leaders of Boko Haram are apparently pitted against each other in a power struggle within Islamic State’s west African affiliate.

Isis announced on Tuesday that the group that has ravaged northern Nigeria for the past seven years had a new leader – Abu Musab al-Barnawi. An Isis magazine carried an interview with him and said he was previously a Boko Haram spokesman.

However an audio message apparently recorded by Abubakar Shekau, the long-time leader of Boko Haram, who has appeared in many of its videos, was released on Thursday denying al-Barnawi’s claim. In the recording, a man who said he was Shekau said that he was still in control of the armed terrorists whose most notorious crime was the abduction of around 300 schoolgirls from their dormitory two years ago, leading to the Bring Back Our Girls campaign led by Michelle Obama.

Shekau has overseen the brutal and bloody growth of the group: since he became Boko Haram’s leader in 2009 more than 20,000 people have been killed and 2.2 million driven from their homes. Thousands have been raped, abducted and enslaved.

According to some analysts, Isis rejected Shekau because of Boko Haram’s deadly attacks on Muslims . More than 40 people were killed in a attack in July last year on a mosque and a Muslim restaurant in the central city of Jos in one of a spate of incidents.

Boko Haram announced in March last year that it was Isis’s west African affiliate, switching allegiance from al-Qaida.

In the recording released on Thursday, the man purporting to be Shekau said that al-Barnawi was “an infidel” preaching “false creeds”. He said Isis’s announcement was a coup. “Today, I woke up to see one who is an infidel whom they want me to follow. No, I won’t ... We cannot subject ourselves to people who are in ignorance of all holy books and teachings,” he said in a speech, which was posted on social media.

In the struggle for control Boko Haram factions could turn on each other, further splitting the insurgents who have been beaten back from their strongholds in northern Nigeria over the past year, mainly since the election of President Muhammadu Buhari.

An audio message that has been circulating in Maiduguri, Boko Haram’s “spiritual home”, says that the group’s third-in-command, a man known as Mamanmunari, had reported Shekau to the head of Isis for “killing his own members, particularly commanders, who are fighting for him just because they questions his attacks on mosques and markets … they tried to persuade Shekau to desist from giving orders to kill their fellow Muslims … but Shekau refuses.”

This message is believed to have led to the Isis announcement.

Freedom Onuha of the National Defence College was among experts who warned that it was difficult to verify that it really was Shekau speaking in the recording. However, he said he was not surprised that Isis would want to replace him. “Most of his members frown at the move to kill fellow Muslims. They, being the moderates, believe that any Muslims should not be targeted, unlike Shekau, who has never hidden that he is of the Takfir. Takfirism is a dangerous strand of salafi jihadi ideology.”

A UN security expert based in Maiduguri said that “massive movement” of the group around the borders between Nigeria, Chad and Niger in the past few weeks and new attacks on the army and a UN convoy suggested that its top echelons have been reorganised. “This suggests that there has been some renewed vigour in them. So it wouldn’t be a surprise that the leadership has changed,” he said.

(The Guardian)