The use of children as suicide bombers by the insurgents of Boko Haram has surged in 2017, the United Nations Children's Fund said on Wednesday.

In the countries fighting Boko Haram in the Lake Chad region — Nigeria, Niger, Cameroon and Chad — 27 children have been used in suicide attacks by the armed Islamist group in the first three months of the year, UNICEF said in a report and statement.

There were nine cases in the same period last year, and 30 children used for bombings in all of 2016, it said. Most were girls.