The global rights watchdog urged Nigeria to release the children – some as young as five years – detained in degrading and inhuman conditions in military cells, in a report rejected by the Nigerian army.
More than 40 people were also wounded when three unidentified bombers struck in the northeast state of Borno where villagers were watching a football match on TV, officials and villagers say.
Many Nigerian women who were once married to Boko Haram fighters are navigating their trauma, though by not denying their experiences. They also want to raise their children in anonymity, hoping their true identity is never revealed.
The attack was carried out in Kareto village, 335 kilometres north of the Borno state capital Maiduguri, military officials say.
Army spokesman Ezindu Idima said in a statement government troops "had a fierce encounter" before thwarting the militants who came in large numbers to loot food items and other valuables.
Some hours before the opening of polls on Saturday, multiple explosions rocked the northeastern city of Maiduguri, perhaps in a daring attempt to breed fear and discourage voting.
Nigeria counts votes in closely-fought presidential election even as voting continues in some units where polling opened late or ballot machines malfunctioned.
Military sources said the attack targeted the Forward Operation Base in Ngwom village, some 14 km north of the Borno state capital, Maiduguri.
In the city of Maiduguri, where the militant group was formed, Islamic scholars and community leaders are trying to contain the group's violent message with a curriculum based on peace.
The released children were among 1,175 boys and 294 girls who had been identified as being associated with the Civilian Joint Task Force in the city of Maiduguri, UNICEF said, although the total has yet to be verified.
With tens of thousands of people fleeing Boko Haram atrocities and taking refuge in urban centres, real estate prices have spiked, allowing developers to make huge profits.
Two blasts ripped through the town of Damboa in Borno state on Saturday evening targeting people returning from celebrating the Eid al Fitr holiday, in an attack bearing all the hallmarks of Boko Haram.
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