From Amnesty International:
Approximately 250,000 children under the age of 18 are thought to be fighting in conflicts around the world, and hundreds of thousands more are members of armed forces who could be sent into combat at any time. Although most child soldiers are between 15 and 18 years old, significant recruitment starts at the age of 10 and the use of even younger children has been recorded.
Around the world, children are singled out for recruitment by both armed forces and armed opposition groups, and exploited as combatants. Easily manipulated, children are sometimes coerced to commit grave atrocities, including rape and murder of civilians using assault rifles such as AK-47s and G4s. Some are forced to injure or kill members of their own families or other child soldiers. Others serve as porters, cooks, guards, messengers, spies, and sex slaves.