In one of these cases the munitions were air-dropped, leading the activists to conclude that the Saudi-led coalition was behind the attack, which wounded three people. The coalition is the only party to the Yemeni conflict that uses aircraft.
"The Saudi-led coalition and other warring parties in Yemen need to recognize that using banned cluster munitions is harming civilians," HRW’s senior emergencies researcher Ole Solvang said.
HRW also said that they have received information suggesting other possible incidents of cluster munitions use.
More than 100 countries have signed the 2008 Convention on Cluster Munitions, but neither Saudi Arabia nor Yemen are parties to the international treaty prohibiting the use of cluster bombs.
The Saudi-led coalition began carrying out airstrikes on the Houthi position in Yemen in late March at the request of displaced Yemeni President Abd Rabbuh Mansur Hadi.