Boys carry bows and arrows in Kerawa, Cameroon, an area near the Ni­ger­ian border that has faced frequent Boko Haram attacks. (Joe Penney/Reuters)

In the last two years, Boko Haram militants have increasingly turned to a new tactic in their attacks in West Africa: child suicide bombers.

The number of children involved in such blasts grew more than tenfold, from four in 2014 to 44 in 2015, according to a report released by the U.N. children’s agency on Tuesday. And more than three-quarters of the children are girls — some as young as 8 years old.

The accounts by UNICEF add another chilling view into the atrocities blamed on the Boko Haram group, which has conducted mass kidnappings of children, including more than 200 school girls abducted from a boarding school in northern Nigeria two years ago.

Some girls and women who escaped have claimed that captives face sexual abuse and forced marriages.

Map: The brutal toll of Boko Haram’s attacks on civilians

“Let us be clear: These children are victims, not perpetrators,” said Manuel Fontaine, UNICEF’s regional director for West and Central Africa, in a statement. “Deceiving children and forcing them to carry out deadly acts has been one of the most horrific aspects of the violence in Nigeria and in neighboring countries.”

Offensives by security forces in Nigeria, Cameroon and Chad have forced the Islamist group from most of the territory it once controlled. In response, Boko Haram has conducted a growing number of attacks on civilian targets, killing hundreds of people in recent months.

The report also reflects Boko Haram’s push in recent years outside its former strongholds in northern Nigeria. Nearly half the child suicide attacks, 21, were in neighboring Cameroon, it said.

But both Nigerian officials and international aid groups have struggled to explain the reason for the surge in child attackers.

Although young suicide bombers are used in other conflict zones, the rise in Boko Haram’s case is stunning. Since 2014, 20 percent of all suicide bombings carried out by the group have been children, according to UNICEF.

Some of the children were abducted by Boko Haram from their homes, and their bodies were identified months later from remains after suicide attacks. Last month, a young girl blew herself up in a mosque in the northern Ni­ger­ian city of Maiduguri, killing at least 22 people. Her identity has not yet been determined.

The Nigerian military, for its part, has come to treat children abducted by Boko Haram as threats no different from adults. Boys have appeared on “wanted posters” across northeastern Nigeria — once the stronghold for the group — along with dozens of top Boko Haram suspects.

Women who escaped from forced marriage and sexual slavery at the hands of Boko Haram talk about their abductions, and the hard transition back to life in Nigeria after they found freedom. (Human Rights Watch)

“Banditry knows no age,” said Maj. Gen. Lucky Irabor, the top military official in the northeast, when a Washington Post reporter asked about the boys on the poster.

But according to UNICEF, many of the attacks are conducted involuntarily. “Boys are forced to attack their own families to demonstrate their loyalty to Boko Haram,” the report said.

Hundreds of girls, meanwhile, have been taken captive by the group.

“The calculated use of children, who may have been coerced into carrying bombs, has created an atmosphere of fear and suspicion that has devastating consequences for girls who have survived captivity and sexual violence by Boko Haram in North East Nigeria,” said UNICEF’s report.

In a separate report from Human Rights Watch released Tuesday, researchers said that “Nigeria’s security forces have contributed to the problem by using schools as military bases, putting children at further risk of attack from the Islamist armed group.”

Human Rights Watch also reported that “at least 611 teachers have been deliberately killed.”

Nearly 1.3 million schoolchildren have been displaced by the conflict, according to UNICEF, including 5,000 children separated from their parents.

And violence is not the only threat facing children in the region. By January, 195,000 children were suffering from severe acute malnutrition.