Both Hezbollah and Israeli forces fired cluster munitions during the recent conflict in Lebanon, according to the group Human Rights Watch.
The Israeli Arab village of Mghar was hit several times in the war
The Islamist militant movement used far fewer cluster weapons than Israel, HRW says, with only two strikes confirmed.
They were the first known deployments of a Chinese-made Type-81 rocket anywhere in the world, the group says.
But a Hezbollah MP denied the group had used cluster munitions, telling the BBC the accusations were false.
"We did not use these bombs. We don't have them. And we reject the use of these bombs anywhere in the world because they hurt civilians, especially when dropped on residential areas. Our stance is consistent. It can never change," Hassan Hoballah said.
Israel has been heavily criticised for its extensive use of cluster weapons around civilian areas in Lebanon.
Cluster weapons spray out numerous smaller bomblets, or submunitions, some of which do not explode immediately, becoming de facto landmines that continue to pose a danger after the end of the fighting.
HRW says two 122mm Type-81 rockets hit the Arab village of Mghar in northern Israel on 25 July, nearly two weeks after the beginning of conflict.
"Use of cluster munitions is never justified in civilian-populated areas because they are inaccurate and unreliable," said Steve Goose, director of the group's Arms Division.
Their first use during the conflict by Israel was documented by HRW on 19 July in the village of Blida, killing a 60-year-old woman and injuring 12 other civilians.
Israeli police told the group that they had documented 113 cluster rockets fired at Israel, causing one death and 12 injuries.
HRW says until now Israel prevented publication of the details for security reasons.
There are up to 1m unexploded Israeli submunitions in Lebanon from the summer's bombardment, the United Nations says.
They cause an average of nearly three civilian casualties a day in Lebanon, including 15 fatalities since the 14 August ceasefire.