Nigerian Islamist militant group Boko Haram has threatened to "sell" the hundreds of schoolgirls it abducted three weeks ago. Militant leader Abubakar Shekau sent a video obtained by the AFP news agency, in which he said for the first time that his group had taken the girls. About 230 girls are still believed to be missing, prompting widespread criticism of the Nigerian government. The Boko Haram insurgency has left thousands dead since 2009. The girls were taken from their boarding school in Chibok, in the northern state of Borno, on the night of 14 April.