The Nigerian army on Monday released 183 children after clearing them of any ties to Boko Haram, Unicef said in a statement. 
The children, aged between seven and 18, were released in Maiduguri, the capital of northeast Borno state, after being detained and investigated for any links with the jihadists. 
"These 8 girls and 175 boys are first and foremost victims of the ongoing conflict and their release is an important step on their long road to recovery," said Mohamed Fall, Unicef's representative in Nigeria.
The statement did not say how long the children had been detained.
Boko Haram's nine-year-old fight to establish a hardline Islamic state has claimed at least 20,000 lives and displaced more than two million people.
Children have been targeted by the Islamists, who recruit boys and girls and indoctrinate them in order to replenish their ranks. In April, Unicef said over 1,000 minors had been abducted since 2013.
The military has been criticised by human rights organisations for conducting mass arrests of people suspected of ties with the group. 
Amnesty International said in a 2018 report that the military had held "thousands of young men, women and children" in detention centres across the country. 
It said there were over 4,000 people in Giwa barracks, located in Maiduguri, held in "extremely overcrowded cells" where "disease, dehydration and starvation were rife".