The students' release also comes amid pressure from the girls' families on the Nigerian government to secure their freedom from whomever still held them.
"At this moment, I am very, very excited", he said by phone from Maiduguri.
Osinbajo said the girls will still be in care of the government for sometime before they are allowed to leave with their parents.
"When you are fighting an insurgency, it's a combination of carrot and stick", Mohammed said.
Jonathan who has been vocal on many other issues has chosen to be silent on the release of the Chibok girls. "But it could mean a new phase in the conduct of the war against terror".
Boko Haram kidnapped almost 300 girls from a secondary school in the Borno state town of Chibok in April 2014.
"About 100 more (girls) are still in the hands of the terrorists".
Meanwhile, Ewi warned that if the recent release of the girls were due to the reported release of four Boko Haram fighters, then "this could also be indirectly assisting the insurgent group".
A Nigerian hostage negotiator who was not involved in Thursday's release told The Associated Press a "handsome ransom" in the millions of dollars was paid by Switzerland's government on behalf of Nigerian authorities.
A note from Washington, D.C., dated May 15, detailed concerns voiced by US officials at a Senate committee hearing about Nigeria's response to the Boko Haram threat.
UNFPA, the United Nations Population Fund, welcomes the release of 21 Chibok schoolgirls who were captured by Boko Haram.
President Muhammadu Buhari's government said, Nkeki was being in the special locked up secret service where she was getting medical care and trauma counseling.
"Please note that this is not a swap", said Information Minister Lai Mohammed.
A Boko Haram insider told CNN in August that despite the leadership split, longtime leader Abubakar Shekau still controlled the Chibok girls and was thought to be hiding in the forest.
The Boko Haram crisis continues to pose a major human security challenge in Nigeria.
On Thursday, the heads of the armies of Nigeria, Chad, Niger, Cameroon and Benin, met in the Niger capital Niamey to discuss a "final assault" on the jihadists.
Campbell pointed out, however, that Boko Haram has not been defeated. Yet more than a year on, the group continues to control swaths of territory across northeastern Nigeria and has proved resilient in the face of shifting military tactics deployed against it.
More than 20,000 people have died and 2.6 million have been driven from their homes in Boko Haram's seven-year insurgency aimed at creating an Islamic state across the West African oil producer, whose 170 million people are divided nearly equally between Muslims in the north and Christians in the south.
Five men were charged in the same court for attempting to kill the same complainant.