The number of child bombers used by the Islamic extremists of Boko Haram has increased from four to 44 in a year - with devastating consequences in communities that now see children as threats, Unicef said.
Some 75 % of the children used are girls, a new report said, emphasising that these children, many believed captives, are "victims, not perpetrators".
"As 'suicide' attacks involving children become commonplace, some communities are starting to see children as threats," said Manuel Fontaine, West Africa director of the UN children's agency.
"This suspicion toward children can have destructive consequences: How can a community rebuild itself when it is casting out its own sisters, daughters and mothers?"
The number of children involved in suicide attacks in Nigeria and neighbouring Cameroon and Chad rose 10-fold last year, with the frequency of all suicide bombings increasing from 32 in 2014 to 151 last year, Unicef said.
In 2015, 89 of these attacks were carried out in Nigeria, 39 in Cameroon, 16 in Chad and seven in Niger, the report said.
Boko Haram has sent bombers to mosques, market places and other soft targets since a multi-national military offensive forced them out of a large swath of the country that they held until a year ago.
Boko Haram wants to create an Islamic caliphate in Nigeria, Africa's biggest oil producer whose 170 million people are divided almost equally between Christians mainly in the south and Muslims in the north.
Another new report, from Mercy Corps, found unemployment was not a leading reason for young people to join Boko Haram, as has been assumed. The study, based on interviews with 47 former members, did point to a financial motivation, however.
"Boko Haram has exploited common desires of youth ... to get ahead economically," said the report from the Portland, Oregon-based charity.
"Many youth described either accepting loans prior to joining or joining with the hope of receiving loans or capital for their mostly small, informal businesses."