Some 276 girls were abducted from their school in 2014
Islamist militant group Boko Haram has released 21 schoolgirls who they abducted in April 2014.
The girls from Chibok were released into the custody of the Nigerian government.
The names of the released girls are to be published soon.
Some 276 girls - mostly aged between 16 and 18 - were abducted from their school.
The kidnapping led to international condemnation, with US First Lady Michelle Obama among those joining a campaign with the hashtag: #BringBackOurGirls.
AFP reports the girls were released as part of a prisoner swap deal.
It followed negotiations between Boko Haram, the International Red Cross as well as the Swiss and Nigerian governments.
Mallam Garba Shehu, the official spokesman to the Nigerian president, said: "It is confirmed that 21 of the missing Chibok Girls have been released and are in the custody of the Department of State Services.
"The release of the girls, in a limited number is the outcome of negotiations between the administration and the Boko Haram.....brokered by the International Red Cross and the Swiss government.
"The negotiations will continue," Shehu added.
The group had previously said that the girls would not be released until the government released Boko Haram prisoners.
Earlier this year, the Nigerian army confirmed that one of the girls had been rescued while a second was freed in May.