The U.N. children's agency reports an "alarming spike" in suicide bombings by girls and women used by Boko Haram in northeastern Nigeria.

It says women and children carried out three-quarters of the 26 suicide attacks reported in 2014 and the 27 seen in just the first five months of this year.

UNICEF said Tuesday that kids are "being used intentionally by adults in the most horrific way."

It's not known how many thousands of children and women have been kidnapped by Boko Haram, with new abductions reported every week. UNICEF estimates 743,000 children have been uprooted by the nearly 6-year-old Islamic uprising, with as many as 10,000 separated from their families in the chaos.

The agency is concerned children will be perceived as potential threats and in danger of retaliation.