A teenager who surrendered before carrying out a suicide bombing attack in northern Cameroon says she is one of the Chibok girls abducted from a Nigerian boarding school nearly two years ago.

Idrissou Yacoubou, the leader of a Cameroonian self-defense group, said Saturday that the girl is about 15 years old and turned herself in before detonating her explosives.

He described her as "tired, malnourished and psychologically tortured."

Dozens of the Chibok girls were last seen in a video alongside the leader of Boko Haram, who has pledged his allegiance to the Islamic State.

The plight of the more than 200 girls still missing has remained a mystery, though many have feared they were married off to fighters or are being used as suicide bombers for the extremist group.