The Islamist militant group Boko Haram is reported to have kidnapped more than 200 girls in Nigeria last month, but little is known about the group's leader, Abubakar Shekau.
In a series of videos posted online, Shekau admits to kidnapping the girls and says he will sell them. "Allah says I should sell. He commands me to sell."
Boko Haram has received worldwide attention for the mass kidnapping, with many celebrities and public figures tweeting the #BringBackOurGirls hashtag in support of efforts to find the girls.
The anti-Western group has been active since 2009, and is also suspected of killing hundreds in an attack on a Nigerian village earlier this week.