Children were used as suicide bombers in a triple attack in Nigeria on Monday, Unicef has said. Two girls and a boy carried out the bombing outside a video hall in Konduga village in north-eastern Borno State, the UN children's charity said. Their ages are not yet known. Officials say at least 30 people were killed and 40 injured in the attack. The bombing is believed to have been carried out by the Boko Haram jihadist group. It has not yet commented. According to Unicef, five children have been used in suicide attacks since the beginning of the year. In 2018, 48 children were used as human bombs in Nigeria, including 38 girls. "Unicef appeals to all those involved in this terrible conflict to protect children at all times and to keep them out of harm's way," the organisation said. Formed in Borno State, Boko Haram has waged a brutal insurgency across the north-east for a decade. As part of the ongoing armed conflict, thousands of children have been recruited and used by armed groups as combatants and non-combatants. Unicef said girls are raped and forced to marry, with some becoming pregnant in captivity and giving birth without medical care.