Kano - In-fighting has broken out in Boko Haram after the Islamic State group announced a new leader of its Nigerian affiliate, according to reports in the country's remote northeast.IS said last month that Abu Musab al-Barnawi, the son of Boko Haram's founder Mohammed Yusuf, had replaced Abubakar Shekau at the head of the designated terrorist organisation.But Shekau then insisted he was still in charge of the Islamist group, whose insurgency has killed at least 20 000 people since 2009 and forced more than 2.6 million from their homes.Sources in northeast Nigeria now say there have been deadly skirmishes between the two factions, even as Nigeria's military seeks to finally rout the rebels in a sustained counter-offensive.Last Thursday, several fighters from Shekau's camp were said to have been killed in two separate gun battles with IS-backed Barnawi gunmen in the Monguno area of Borno state near Lake Chad.Nigeria's military declined to comment on the reported in-fighting when contacted by AFP.'True jihad'Mele Kaka, who lives in the area, told AFP: "The Barnawi faction launched an offensive against the Shekau faction who were camped in the villages of Yele and Arafa."In Yele, the assailants killed three people from the Shekau camp, injured one and took one with them, while several were killed in Arafa," he said by telephone from the state capital, Maiduguri. The attack prompted residents of Arafa to flee, he added.Fighters from Barnawi camp had the previous day attacked gunmen loyal to Shekau in Zuwa village in nearby Marte district, killing an unspecified number, Kaka said. "The Barnawi fighters told villagers after each attack that they were fighting the other camp because they had derailed from the true jihad and were killing innocent people, looting their property and burning their homes," he went on. "They said such acts contravene the teachings of Islam and true jihad."Ideological splitShekau has led Boko Haram since the death of Mohammed Yusuf in police custody in 2009, waging a deadly, indiscriminate guerilla war that has overwhelmingly targeted civilians.Suicide bombers have repeatedly hit busy mosques, churches, markets and bus stations while hit-and-run raids have destroyed remote villages, killing and maiming residents.Thousands of people, many of them women and young girls, have been kidnapped, including more than 200 schoolgirls, who were seized from the Borno town of Chibok more than two years ago.Shekau has justified the attacks in ranting video and audio monologues against the secular state, those who support it and anyone who does not share his radical interpretation of Islam.He pledged allegiance to IS leader Abu Bakr al-Baghdadi in March last year, changing the group's name to Islamic State West Africa Province (ISWAP).Experts, however, suggest the indiscriminate slaughter of civilians as well as Shekau's "dictatorial" style, including secret killings of dissenting commanders, have caused a rift.Shortly after his nomination, Barnawi made a pointed critique of Shekau's leadership, lambasting him for targeting ordinary Muslims.Gun battleNews of the factional clashes have been slow to emerge because of the destroyed telecommunications infrastructure in northeast Nigeria, and restricted access.A civilian vigilante assisting the military against Boko Haram said there were sporadic clashes between the opposing fighters.The three incidents described by Kaka were "very possible", said Babakura Kolo. "I don't have news of the clashes but it is not surprising if they did occur because there has been similar in-fighting among the two Boko Haram camps," he added. Two weeks ago, there was a fierce gun battle in the Abadam area of Borno state, near the border with Niger, where Shekau's fighters were routed, he said."It was a deadly fight and Shekau's fighters were forced to flee," he said.Hundreds of residents of the villages and their herds taken hostage by the fleeing fighters were allowed to go about their normal lives by the Barnawi faction, Kolo added.