The sources disclosed that the girls were picked up by military helicopter from Banki area of Borno state where Boko Haram militants dropped them off earlier today.
The release of the 21 girls comes as President Buhari began a three-day trip to Germany to discuss assistance for the rebuilding of the northeastern part of Nigeria ravaged by Boko Haram.
Newsmen could not immediately obtain the names of the girls released today.
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