Abuja - Nigerian President Muhammadu Buhari said Sunday that Boko Haram leader Abubakar Shekau is "wounded", in his first comments on military claims that the jihadi leader was injured in an attack.Nigeria's armed forces said on Tuesday that Shekau had been wounded in an air strike on Boko Haram's forest stronghold, but released no further statement or evidence confirming his condition."We learnt that in an air strike by the Nigeria Air Force he was wounded," Buhari said in a statement from Nairobi, where he is attending a development conference."Indeed their top hierarchy and lower cadre have a problem," Buhari said. "They are not holding any territory and they have split to small groups attacking soft targets."Buhari said that Shekau had been "edged out" of the group, adding credence to claims that Islamic State (IS)-appointed Abu Musab al-Barnawi was now in charge of the insurgency.Power struggleSigns of a power struggle in the top echelons of the jihadi group appeared earlier this month when Shekau released a video denying he had been ousted.Barnawi is believed to be the 22-year-old son of Boko Haram founder Mohammed Yusuf and was announced as the group's leader in August by ISIS.Buhari made his remarks from Nairobi this weekend where he is attending the Tokyo International Conference on African Development, a summit designed to boost ties between Africa and Japan.The president also said he "is prepared to talk to bona fide leaders of Boko Haram" to negotiate the release of 218 Chibok girls captured by the militants in 2014.Boko Haram has ravaged northeast Nigeria in its quest to create a fundamentalist Islamic state, killing over 20 000 people and displacing 2.6 million from their homes.Oil battle Turning to another major security concern in Nigeria, Buhari threatened militants sabotaging oil infrastructure in the southern swamplands of the Niger delta. "We will deal with them as we dealt with Boko Haram if they refuse to talk to us," Buhari said. The country's petroleum minister has said that as a result of the ongoing attacks Nigeria's oil output has dropped 23% from last year to 1.5 million barrels per day, according to Bloomberg News. Groups including the Niger Delta Avengers are demanding a greater share of oil revenues, political autonomy, and infrastructure development in the southern riverlands where despite massive oil wealth people still struggle to access basic health care and education. Buhari said his government was in talks with the some of the militants but said there was no "ceasefire", despite an announcement by the Avengers last week.