Women and girls kidnapped by the Nigerian Islamist group Boko Haram are raped and forced to marry fighters even if they are underage, according to testimonies from women who have escaped the group.

In its latest report, “Those Terrible Weeks in the Camp: Boko Haram Violence Against Women and Girls in Northeast Nigeria,” New York-based Human Rights Watch estimates that the militant group has abducted about 500 women and girls from Northern Nigeria since 2009. Earlier this year Boko Haram kidnapped 276 girls from a secondary school in the town of Chibok in the northeast of the country. The mass abduction drew international outrage and sparked a viral social media campaign fuelled by the hashtag #bringbackourgirls. Human Rights Watch spoke to 12 of the 57 of the girls who have escaped; 219 are still missing.

Human Rights Watch explains that Boko Haram leader Abubakar Shekau has taken responsibility for abducting women and girls, and has justified the kidnappings as retaliation for the detention of Boko Haram family members held by the Nigerian government. In a 2012 video, Shekau says: “Since you are now holding our women, just wait and see what will happen to your own women … to your own wives according to Sharia law.”