Twenty-one of the Chibok schoolgirls kidnapped by Boko Haram have been freed, a senior Nigerian government official has told the BBC.

It is thought that they are now with the security services in the north-eastern city of Maiduguri.

It is not yet clear how the girls were rescued.

The Islamist militant group kidnapped more than 250 students from a school in Chibok in April 2014 – an act that provoked international condemnation.

More soon

Source BBC