"As fighting rages in Yemen, the Houthis have ramped up their recruitment of children. Commanders from the Houthis and other armed groups should stop using children or risk prosecution for war crimes," Fred Abrahams, a special adviser at the Human Rights Watch, said.
Houthis use children as scouts, guards, runners and fighters, the HRW said, adding that some end up injured and killed in battle.
According to the human rights watchdog, Houthis are not the only insurgent group to send children into battle. Al-Qaeda in the Arabian Peninsula (AQAP) is also deploying child soldiers, HRW said.
The deterioration of the political situation in Yemen has led to a rise in AQAP's activity. The al-Qaeda offshoot is mostly active in the south of the country.
According to UNICEF, as many as 140 child soldiers had been recruited as soldiers in Yemen between March 26 and April 24.