"Hezbollah's deployment of the Chinese-made Type-81 122mm rocket is also the first confirmed use of this particular model of cluster munition anywhere in the world," said the group, adding it documented two Type-81 cluster strikes on July 25 in the village of Mghar in northern Israel.
The report said while Hezbollah used far fewer cluster munitions than Israel in the conflict, the findings raise serious concerns about the proliferation of such weapons to non-state armed groups, as well as states.
"We are disturbed to discover that not only Israel but also Hezbollah used cluster munitions in their recent conflict, at a time when many countries are turning away from this kind of weapon precisely because of its impact on civilians," said Steve Goose, director of Human Rights Watch Arms Division.
"Use of cluster munitions is never justified in civilian-populated areas because they are inaccurate and unreliable."
Human Rights Watch said it is not known when and how Hezbollah obtained the foreign-made cluster munitions.