According to the UNICEF, it was not immediately clear how long the children had been held because the army often detains civilians to check whether they have links to Boko Haram militants.

"We fear there are still kids who are being at least temporarily detained because they are being released from Boko Haram areas by the army but then kept for a while," Manuel Fontaine, the UNICEF's regional director for Western and Central Africa, told reporters on Friday.

"Once we get children out, there is a major issue of stigmatization in the communities…There is a sense that children who have been associated with Boko Haram for a while, could be, and in some cases we have some evidence, rejected by community and people around them." Fontaine added.

He said this was also a problem for girls from the town of Chibok who had been kidnapped by the Boko Haram and later returned to their families. Earlier this month, Nigerian officials secured the release of 21 girls out of the 200 that were taken away by the terror group from their school in Chibok in 2014.

Thousands in army custody

There was no comment from the army following the release of the children. Military officials have said they need to question civilians to check whether they have any links to Boko Haram. The militant group has been trying to establish an Islamic state in northeastern Nigeria's Borno state and its capital, Maiduguri, for the last seven years. The terror group often uses women and children as suicide bombers to stage attacks.

According to Amnesty International, some 8,000 detainees have died while in the Nigerian army's barracks between 2011 and 2015. Earlier this year, the rights group called for the detention center's closure, claiming that babies and children were among those dying because of untreated gunshot wounds, disease and hunger.

Nigerian Defense spokesman Rabe Abubajar denied the charges, calling them a "distraction" and saying the forces' duty was to "protect lives" and that is what they were doing.

Nigerian security forces have gone on the offensive against Boko Haram since 2015, when Muhammadu Buhari took over as Nigeria's president. Neighboring countries, including Chad, Cameroon and Niger have joined in to contain the militants.

So far, the conflict has killed thousands and displaced over 2 million people. UNICEF said around 20,000 children have been separated from their parents and only 5,000 of these had been reunited with their families. 

mg/sms (Reuters, AP)