An investigation by the Malian Coalition for Rights of the Child found children are serving not only as fighters but also scouts, couriers, minesweepers, cooks and servants, Voice of America reported.
The investigation corroborates recent reports by the U.N. Children's Fund that militant groups have recruited hundreds of children.
Tuareg rebels took control of the northern part of the country following a March military coup in the capital, Bamako. Since then, al-Qaida-linked fighters have pushed out the Tuareg and imposed a strict form of Islamic law.
Scores of boys as young as 14 have been trained by the extremists to guard roadblocks and administrative buildings in the occupied town of Gao, residents there told VOA by phone.
The ongoing crisis in Mali has forced about 435,000 people from their homes, the United Nations said.
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