Abuja, London- An alarming number of children have been used by Boko Haram as suicide bombers in the first months of 2017, UNICEF said Wednesday.

Experts said the number of children used in suicide attacks by Boko Haram in public places across Nigeria, Chad, Niger and Cameroon surged to 27 in the first quarter of this year, compared to nine in the same period in 2016 and 30 in the year as a whole – majority of them are girls.

The Boko Haram movement emerged eight years ago and it has since killed more than 20,000 people. It became known globally after abducting 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, and forcing them to become suicide bombers, to help the militants in their conflict or to marry fighters, UNICEF said. Children who escape Boko Haram are often held in custody by authorities or ostracized by their communities and families.

On Monday, Nigeria’s military released 593 people, including children, after clearing them of having ties with Boko Haram. A UNICEF spokesperson told Reuters that about 370 remain in custody.

“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 added in its report.

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

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