"While it is difficult to establish the precise figures, reliable sources have stated that numbers [of children] involved are in the hundreds and appear to be escalating," UNICEF said in a news release.
"UNICEF calls on all parties to the conflict, leaders and community members to ensure that children are protected from the harmful impact of armed conflict and do not participate in hostilities," the U.N. agency said.
Last month, UNICEF reported at least 175 boys, between the ages of 12 and 18, were directly associated with armed groups in the north where fighting between government forces and Tuareg rebels broke out in January.
Recruiting and using children less than 18 years of age by armed groups is prohibited by international law, the children's agency said. Such action also constitutes a war crime and crime against humanity if children are recruited and used under the age of 15, it said.
Instability and insecurity resulting from renewed clashes, the proliferation of armed groups in the region and the political instability following a military coup in March prompted more than 250,000 Malians to flee to nearby countries, the United Nations said. About 174,000 Malians are estimated to be internally displaced.
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