Nigeria's military has told the BBC that some of the schoolgirls abducted from Chibok town in April by Islamist militants have been released.
Army spokesman Brig Gen Chris Olukolade did not give details about the number of girls freed, saying the exercise was "ongoing".
More than 200 girls were kidnapped by Boko Haram fighters from a boarding school in the north-eastern Born state.
It caused worldwide outrage and sparked a social media campaign.
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