If the cluster bombs fail to detect their target, they are designed to self-destruct in the air, or if that fails, to deactivate themselves after a short time. But sometimes those mechanisms don't work, posing a lethal danger for those who later encounter them.
Saudi Arabia says there are only Yemeni forces that Saudi Arabia is supporting, according to Brig. Gen. Ahmed Asiri, a Saudi military spokesman. He told CNN Saudi Arabia has been using CBU-105 in Yemen against armored vehicles and not in the city.
Human Rights Watch included video, marked-up satellite maps and photos in its report.
The video shows delivery devices falling from the sky by small parachutes then deploying its bombs with a burst of black smoke in midair. Shallow explosions spread over areas on the ground below. The images were shot by pro-Houthis in April, HRW said.
The U.S. Department of Defense has said it will stop the transfer to foreign governments of cluster munitions that leave behind more than 1% of their bombs unexploded -- but not until after 2018.
"Saudi-led cluster munition airstrikes have been hitting areas near villages, putting local people in danger," Steve Goose, the director of HRW's arms division, said in a statement. "These weapons should never be used under any circumstances."
The human rights activists say the cluster munitions were dropped over northern Saada governorate, a Houthi stronghold near Saudi Arabia. The satellite map shows the target area in the mountains above the villages of al-Ssam and al-Safraa.
About 5,000 people live in al-Safraa in times of peace, HRW said.Saudi Arabia Used U.S. Supplied Cluster Bombs in Yemen.