Twenty-one of the 218 missing Nigerian schoolgirls abducted in 2014 by the extremist group Boko Haram have been released, according to Nigeria's government.
According to presidential spokesman Mallam Garba Shehu, the girls were were released Thursday in northern Borno state, rescued by a military helicopter and transported to the state capital, Maiduguri.
Shehu said the girls were released as a result of negotiations with the militant group, brokered by the International Committee of the Red Cross and the Swiss government. It is the first major breakthrough since the girls' kidnapping in April 2014.
Shehu said the girls were exhausted and were being given the opportunity to rest. Their names would be released shortly, he added.
President Muhammadu Buhari was due to leave Nigeria for Germany on an official visit shortly after the news broke.
"The president (Muhammadu Buhari) welcomes the release of the girls but cautioned Nigerians to be mindful of the fact that more than 30,000 fellow citizens were killed by terrorism," Shehu said in a statement on Twitter.
Nearly 200 girls are still missing, some believed to have been killed in Nigerian air force strikes on militants' positions. Shehu said negotiations were continuing to secure the release of the others.
Before the latest release, only one of the missing 219 schoolgirls kidnapped from the town of Chibok had been freed. Amina Ali Nkeki was found in May with her Boko Haram husband in the Sambisa forest, a stronghold of the extremist militia.
Ayuba Alamson, the guardian of four nieces who were kidnapped, expressed joy that the 21 girls were released and called on Boko Haram to free the remainder and enter into peace talks with the government.
"At this moment, I am very, very excited," he said by phone from Maiduguri. "I am full of happiness.
"It's what we have been expecting would happen for a long time now. If the government won't do it, God will do it. We are continuing to pray that God will open the way for all of them to come back."
He said it was time for Boko Haram "to repent the violence it has caused to humanity. It's high time for them to repent and start dialogue with the government.
"I ask now to please release the girls because none of these girls are government politicians or government officials. They're from ordinary poor families who just farm to feed themselves."
Alamson said even though his four nieces may not be among those released, he was still overjoyed that at least some of the abducted girls had been freed.
The 276 girls initially abducted were sleeping at a school in preparation for examinations, at a time when Boko Haram had been targeting schools, killing teachers, firebombing dormitories and warning schools to close.
Several dozen escaped, but the remaining 219 were taken into the Sambisa forest by gunmen.
The group's leader, Abubakar Shekau, announced in a video shortly afterward that the girls were "slaves."
Like thousands of other women and girls abducted in northern Nigeria in recent years, the girls are believed to have been forced into marriage with Boko Haram fighters.
The Islamist extremists, allied to Islamic State, have lost most of their territory in recent months but are still capable of carrying out deadly attacks, the latest a suicide bombing in Maiduguri on Wednesday that killed eight people and has been blamed on a female suicide bomber.
The Chibok mass kidnapping, which triggered a global hashtag campaign #BringBackOurGirls on Twitter, was the second-largest, after a mass abduction in Damasak in 2014, where at least 400 people, mostly schoolchildren, were abducted.
