Nigerian President Muhammadu Buhari has acknowledged setbacks in the fight against Boko Haram, as the jihadists launched fresh attacks in the restive northeast.The 76-year-old head of state was elected in 2015 on a promise to end the Islamist insurgency, which has killed more than 27,000 people since 2009 and left 1.8 million homeless.But as he seeks a second term in elections next month, a wave of attacks, including against military bases, has undermined his repeated claim that the group is virtually defeated.Soldiers have also complained that Boko Haram fighters are better armed and that morale is low, particularly because of a lack of rotation and support.In a recorded interview broadcast late on Monday on Arise TV, Buhari conceded that troops had come under pressure from the Islamists' guerrilla warfare.Buhari, a former army general who became military ruler after ousting the elected government in a coup in 1983, said the "question of morale is correct".Efforts were being made to address the issue, he said.Relentless hit-and-run raids, as well as suicide bomb attacks, were hard to deal with by conventional means, he argued."There is really what I would call battle fatigue," he said, adding that retraining would help combat the jihadists' tactics.On Monday evening, fighters loyal to factional leader Abubakar Shekau attacked Sajeri village on the outskirts of the Borno state capital, Maiduguri, killing three people.At the same time, militants aligned to the Islamic State group-backed Boko Haram faction attacked a military facility in Auno, some 23km south of the city.The increase in attacks has seen the appointment of five different commanders of the military operation against Boko Haram in the last two years.But Buhari has refused to sack his military top brass, unlike his predecessor Goodluck Jonathan, who removed senior officers as the jihadists began taking over territory."I accept responsibility for that," Buhari said in the interview, adding that he was "measuring the options very critically".But he said that such appointments were not to be taken lightly."My understanding of security is that when you have a case of emergency you have to be careful with the head of (the armed) services," he said.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.