Armed opposition groups in Syria are using child soldiers in front-line combat positions, Human Rights Watch said.
Groups such as Isis, currently gaining territory from the Iraqi army in neighbouring Syria, have been "aggressively" enticing teenage boys to join their ranks as they attempt to topple Assad.
Zama Coursen-Neff, from the Children's Rights Division of Human Rights Watch said:
"Extremist groups, have aggressively targeted children and enticed them to join.
"It is bad enough that the Syrian government is dropping bombs on children. Armed opposition groups in Syria should not in turn be sending children into harms way".
Human Rights Watch spoke to several current or former child soldiers within Syria, who described their experiences.