The use of children as suicide bombers by the insurgents of Boko Haram has surged in 2017, the United Nations Children’s Fund (UNICEF) 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.

The Boko Haram insurgency is now in its eighth year with little sign of ending, having claimed over 20,000 lives. Its child kidnappings gained global notoriety after the abduction of more than 200 girls from the town of Chibok in Nigeria’s northeast in 2014, three years ago on Friday.

Boko Haram has kidnapped thousands, often raping them, forcing them to become suicide bombers, help the militants in their conflict or marry fighters, UNICEF said.

“These children are victims, not perpetrators,” said Marie-Pierre Poirier, UNICEF’s regional director for West and Central Africa.

“Forcing or deceiving them into committing such horrific acts is reprehensible.”

One 16-year-old girl from Chad lost her legs after being drugged and forced by Boko Haram to take part in an attempted suicide attack on a crowded market, according to UNICEF’s report.

Though the girl survived, her family initially rejected her “out of fear of stigma”.

Children who escape Boko Haram are often held in custody by authorities or ostracized by their communities and families.

About 370 remain in custody, a UNICEF spokeswoman told Reuters, after Nigeria’s military on Monday released 593 people, including children, after clearing them of having ties with Boko Haram.

“Society’s rejection of these children, and their sense of isolation and desperation, could be making them more vulnerable to promises of martyrdom through acceptance of dangerous and deadly missions,” UNICEF said in its report.

Children make up 1.3 million of the 2.3 million people displaced by the conflict.

UNICEF said its response to the crisis “remains severely underfunded”, hitting efforts to provide mental health and social support, reunite families and offer education, safe water and medical services.

Last year, the group received only two-fifths of the $154 million it appealed for.

The United Nations says it needs $1.5 billion in humanitarian aid for the Lake Chad region this year, and $457 million had been pledged for 2017 by late February.