Three suicide bombings by girls aged as young as 10 suggest that Nigeria's Boko Haram has employed a new tactic of forcing abducted children to blow themselves up, experts told NBC News. The girls may be part of the 276 from Chibok who sparked the #BringBackOurGirls social media campaign. Elizabeth Donnelly, assistant head of the Africa program at London's Chatham House think tank, told NBC News that the girls have provided the group with a resource of bombers it sees as completely expendable. "I think it's because these girls just do not matter to them," she said. "They are disposable bodies."