The UN Children's Fund (UNICEF) on Tuesday appealed to the abductors of eight more girls in Nigeria to release them immediately and unharmed, and to those with influence on them to convince them to heed the appeal. "UNICEF calls on the abductors to immediately return these girls unharmed to their communities, and we implore all those with influence on the perpetrators to do everything they can to secure the safe return of the girls -- and to bring their abductors to justice," UNICEF said in a statement. It said the abduction of eight more girls in Nigeria is an "outrage and a worsening nightmare" for the girls themselves, their families, and the families of the more than 200 girls who were abducted in the last several weeks. "That the girls are alleged to have been abducted to prevent them from attending school is especially abhorrent," The statement added. Militant Islamist group Boko Haram claimed responsibility for the girls' abduction and announced in a video yesterday that they would be sold.