Geneva - The United Nations voiced alarm on Tuesday at Boko Haram jihadists' surging use of children, mainly girls, as human bombs in northeastern Nigeria, describing the practice as an "atrocity". The Islamists have for several years been using children to attack crowded markets, mosques and camps for internally displaced people in northeast Nigeria and the broader Lake Chad region.But the UN children's agency said on Tuesday that there had been an appalling increase in the cruel and calculated use of children, especially girls, as so-called "human bombs".Since the beginning of the year, 83 children have been used to carry out bomb attacks in northeast Nigeria - four times as many attacks as in all of 2016, Unicef said in a statement.Fifty-five of the children used as bombers were girls, most of them under the age of 15, 27 were boys and one was a baby strapped to a girl, UN numbers show.Since 2014, a total of 125 children have been used as bombers in northeast Nigeria, according to Unicef. Boko Haram had sometimes, but not always, claimed responsibility for the attacks, the agency added.It stressed that the children used as "human bombs are, above all, victims, not perpetrators." The agency pointed out that the use of children in such attacks had also created suspicion and fear of children who had been released, rescued of had escaped from Boko Haram."As a result, many children who have managed to get away from captivity face rejection when they try to reintegrate into their communities, compounding their suffering," it said.Children in northeastern Nigeria are also struggling to survive a massive displacement and malnutrition crisis, triggered by Boko Haram's bloody insurgency.The violence, which began in 2009, has killed at least 20 000 people and forced some 2.6 million others to flee their homes.Nearly half a million children in the region are at risk of severe acute malnutrition this year alone, Unicef said.