Boko Haram has reportedly released a video appearing to show some Nigerian schoolgirls kidnapped more than two years ago.
The Islamist group took 276 girls from their school in the town of Chibok in April 2014.
More than 200 of them are believed to still be captured.
In the video, a man with his face covered calls on the Nigerian government to release Boko Haram prisoners in exchange for the girls.
