A Nigerian government spokesman confirmed the news.
The girls were among about 220 students abducted from a secondary school in the northeastern town of Chibok in 2014, sparking a global campaign bringbackourgirls supported by then US First Lady Michelle Obama and list of celebrities.
About 21 Chibok were released in October in a deal brokered by Switzerland and the International Red Cross, while a handful of others have escaped or been rescued.
This is the largest single group to be released so far.
But about 195 were still missing.
Last month President Muhammadu Buhari said in a statement that the government was “in constant touch through negotiations, through local intelligence to secure the release of the remaining girls and other abducted persons unharmed”.
The girls were taken from a school in Chibok in the remote northeastern Borno state where Boko Haram has waged an insurgency aimed at creating an Islamic state that has killed thousands and displaced more than 2 million people.