Schoolboys who were abducted in northwest Nigeria were released Thursday, a presidential aide said, although it remained unclear how many. "The abducted students of the Government Science Secondary School, Kankara have been rescued, the Katsina State Government has confirmed the news," Bashir Ahmaad, personal assistant to Nigerian president Muhammadu Buhari said on Twitter. But a security source told AFP that some of the children remained in the hands of their captors. abu-lhd/pvh