Nigeria-based militant group Boko Haram is increasingly using children in "suicide" attacks, a U.N. fund said Tuesday.

Boko Haram used four children in such attacks in 2014 — and 44 in 2015, according to a report from UNICEF. Nearly 1 of every 5 suicide attacks conducted by Boko Haram used a child, and more than two-thirds of the children were girls.

A UNICEF statement puts the word "suicide" in quotes, noting that the children may have carried out the attacks unwillingly.

"These children are victims, not perpetrators," Manuel Fontaine, UNICEF regional director for West and Central Africa, said in that statement.

A UNICEF spokesman told Reuters that in some cases, children might not even know they are carrying a remotely detonated bomb.

The humanitarian organization notes that the use of young girls to carry out suicide attacks also hurts hostages who are freed: It "has created an atmosphere of fear and suspicion that has devastating consequences for girls who have survived captivity and sexual violence by Boko Haram."

As Rachel Harvey of UNICEF said on Weekend Edition in February, many communities worry that girls and women rescued from Boko Haram have been radicalized and are now a threat. Meanwhile, women who were raped by their captors — and especially those who bore children as a result — also face stigma.

"You need strong, influential voices that are going to say, 'We need to accept these girls and women back, and the children. These are victims, it was not their fault,' " Harvey says. She notes that a community's fears that hostages may have been radicalized have to be addressed, not just dismissed.

A separate report released by Human Rights Watch on Monday noted the extent to which Boko Haram has blocked access to education in northern Nigeria.

The group's name means "Western education is forbidden"; the Islamist extremists have targeted teachers and students in attacks, HRW says. The Nigerian government, meanwhile, has used schools "for military purposes," the report finds.

Nearly a million children have been displaced by the violence, with little or no access to education.

A worldwide awareness campaign was launched in 2014 after Boko Haram kidnapped more than 250 schoolgirls from the Nigerian town of Chibok. The hashtag #BringBackOurGirls shot to fame.

Two years later, the girls remain missing — although last month, a girl on an apparent suicide attack mission in Cameroon cried for help and surrendered to authorities, saying she was one of the Chibok girls. It was the first concrete news of the girls' whereabouts in months.

Since the Chibok abductions, thousands of other children have vanished in Nigeria and surrounding countries, UNICEF says.

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