Chibok girls 'forced to join Boko Haram and kill'

The BBC has uncovered evidence that some of the kidnapped Chibok schoolgirls have been forced to join the militant group Boko Haram.

It is claimed some are now being used to terrorise other captives - and are even carrying out killings themselves.

Almost 300 girls were taken from their school dormitories in north east Nigeria, but more than a year on, 219 of them are still missing.

The BBC's Tulip Mazumdar has been speaking to women who were held in the same camps as some of the schoolgirls.