Nigeria's government says the 82 kidnapped Chibok schoolgirls who have been released in an exchange for detained Boko Haram suspects are expected to meet President Muhammadu Buhari on Sunday in the capital.

Buhari's office tweeted the first official confirmation of the largest release of Chibok girls since the mass kidnapping of 276 more than three years ago.

The government says the Swiss government and the International Committee of the Red Cross helped in negotiations with the extremist group. Similar talks led to the first release of 21 Chibok girls in October.

The latest announcement means 113 girls remain unaccounted for. It is feared some were forced to carry out suicide bombing missions for Boko Haram, which has ties to the Islamic State group.