Abubakar Shekau, the head of the Boko Haram Islamist group that kidnapped more than 200 Nigerian schoolgirls last year, has been ousted as its leader, it has been claimed. Shekau, who gained worldwide notoriety after appearing in a series of videos in which he threatened to sell the girls as slaves, has been replaced by another Boko Haram deputy who is said to be open to peace talks, according to President of Chad, Idriss Deby.Deby, whose forces have been fighting Boko Haram militants in Nigeria's border areas, made the comments at a press conference on Tuesday at which he claimed that the group was now on the back foot militarily and would be finished "by the end of the year"."There is someone apparently called Mahamat Daoud who is said to have replaced Abubakr Shekau and he wants to negotiate with the Nigerian government," he said."For my part, I would advise not to negotiate with a terrorist."It was not clear how Deby had obtained his information, although rumours have been circulating recently that Shekau was on the run or had fled Nigeria as a result of increased military operations against Boko Haram. Little seems known as yet about the man named by Deby as his successor, and whose name may well be a nom de guerre."I have not heard of any individual called Mahamat Daoud," said Jonathan Hill, of the Defence Studies Department at London's King's College, who closely monitors Boko Haram. "But there are a number of characters claiming to represent different factions within Boko Haram, and their bona fides are often hard to verify."On Tuesday, a bomb killed at least 47 people and wounded dozens more in the village of Sabon Gari, near the northeast city of Maiduguri. Two days before that, jihadists shot dead four people and abducted five others.While claiming progress in the fight against the jihadists, who have repeatedly hit border areas of Cameroon, Chad and Niger, Deby admitted that suicide bombers still posed a threat. But he added: "Boko Haram is decapitated. There are little groups [of Boko Haram members] scattered throughout east Nigeria, on the border with Cameroon. It is within our power to definitively overcome Boko Haram."It is not the first time reports have emerged claiming Shekau's downfall. Reports from the Nigerian military and media have declared him dead on several occasions, although experts also believe the various videos that have appeared purporting to be him sometimes feature lookalikes. ..