A negotiation has been made on the release of 82 of the more than 200 school girls kidnapped by Boko Haram Islamists about three years ago, securing their freedom in a prisoner swap deal.
The presidency announced that months of talks with the jihadists had "yielded results", just over six months after 21 of their classmates were freed with the help of international mediators.
"Today 82 more Chibok girls were released," it said on Saturday.
"After lengthy negotiations, our security agencies have taken back these girls, in exchange for some Boko Haramsuspects held by the authorities."
No details were given about how many suspects were released or their identities. The girls were to be taken to Abuja today to meetPresident Muhammadu Buhari, the presidency said, thanking security agencies, the Swiss government and the International Committee of the Red Cross (ICRC).
"The president has repeatedly expressed his total commitment towards ensuring the safe return of the Chibokgirls and all other Boko Haram captives," it added.
A military and a civilian militia source in Banki, nearthe border with Cameroon, said "at least 80" girls werebrought to the town late afternoon on Saturday and taken to military barracks.
Shehu Sani, a Nigerian senator who has been involved inprevious negotiations with Boko Haram, told AFP the girls weremostly "in good condition".
The talks lasted for "almost three to four months" and had initially discussed the release of 50 girls but the numberwas later increased, he said.
The government would now look to securing the release ofthe remaining hostages, he added. Boko Haram fighters stormed the Government Girls Secondary School in the remote town of Chibok on the eveningof April 14, 2014 and kidnapped 276 teenaged girls who werepreparing to sit high school exams.
Fifty seven managed to escape in the hours that followedbut the remaining 219 were held by the group. Boko Haram leader Abubakar Shekau, whose fight to createa hardline Islamic state in northeast Nigeria has left atleast 20,000 dead since 2009, claimed in a video message thatthey had converted to Islam.
The audacious kidnapping brought the insurgency to world attention, triggering global outrage that galvanised supportfrom the former US first lady Michelle Obama and Hollywoodstars.
Parents and supporters of the missing girls -- who have become a symbol of the conflict -- last month marked the threeyear anniversary of the abduction, describing the situation asan unending "nightmare".
But they said previous releases had given them strength. Enoch Mark, a Christian pastor whose two daughters wereamong those kidnapped, said he was told of the latest release by the #BringBackOurGirls pressure group and an official inMaiduguri.
He added: "This is good news to us. We have been waiting for this day. We hope the remaining girls will soon bereleased." Boko Haram has used kidnapping as a weapon of war,seizing thousands of women and children, including the Chibokgirls, and forcibly recruiting young men and boys into theirranks.
In a less publicised attack in November 2014, some 300children were among about 500 people kidnapped from the townof Damasak, on the border with Niger, in the far north of Borno state. Most are still missing.
The release of the 21 girls in October last year followedtalks between Boko Haram and the Nigerian government brokeredby the ICRC and the Swiss. Three other girls have also been found.
The first had ababy and was accompanied by a man she said was her husband butthe military said was a Boko Haram suspect. Boko Haram's Shekau has previously said the girls wouldbe released if militant fighters held in Nigerian governmentcustody were freed.
At the time of the release of the 21, Buhari's spokesman Garba Shehu said the government was hoping to secure therelease of 83 others being held by a different Boko Haramfaction.
Last month he said in a radio interview that there wereongoing negotiations involving "some foreign entities" torelease the 195 girls still believed held. He told BBC Hausa the ICRC and Swiss government "have not withdrawn their support in the negotiations".
Other countries were also involved, he added, without elaborating. The ICRC has not yet commented on the latest release. On Friday, Britain and the United States issued asecurity alert warning of a Boko Haram plot to kidnap foreigners in the Banki area, which led to the suspension ofaid flights to the town on Saturday.