Human Rights Watch has accused Saudi-led coalition forces of using cluster bombs that are illegal under international law in its conflict with Houthi rebels in Yemen.

In a statement released on Wednesday, HRW said the coalition troops used cluster munition rockets in at least seven attacks between April and July in Yemen's northwestern Hajja governorate, killing and wounding dozens of civilians.

"Cluster munitions caused civilian casualties both during the attacks, which may have been targeting Houthi fighters, and afterwards, when civilians picked up unexploded submunitions that detonated," it said.

HRW said that it visited four of the seven attack sites in the Haradh and Hayran districts of Hajja, a region bordering Saudi Arabia, in July, and in each of them found unexploded submunitions and remnants of cluster munition rockets.

According to the report, "several of the attacks took place in or near areas with concentrations of civilians", which the group said violates international law.

Local residents named 13 people, including three children, who were killed as well as 22 people who were wounded in the seven attacks, the report said.

Ole Solvang, an HRW researcher, told Al Jazeera that most of the rockets were likely launched from Saudi territory.

Saudi response

In an interview with Al Jazeera, Ahmed Asiri, the spokesman for the Saudi-led coalition, denied use of the specific types of cluster munitions listed by HRW.

Saudi-led coalition spokesman denies use of illegal cluster munitions

He said, however, that not all types of cluster munitions are illegal under international law.

Asiri said the HRW report failed to prove its claims with reliable evidence, saying that the use of "reports from Houthis" was not impartial.

Saudi Arabia has repeatedly said it will only stop its military campaign when it is confident that Houthi rebels no longer pose a threat to its internal security.

HRW called for the UN Human Rights Council to create a commission to investigate war crimes by "all parties" involved in the country's conflict.