The widely banned weapons contain dozens of submunitions, which sometimes do not explode, essentially becoming landmines that can kill or maim long after the initial bomb is dropped.
"The objects are identified as a BLU-108 cluster bomb, manufactured by the US weapons firm Textron, which also produces helicopters, armoured vehicles and car parts."
HRW said in a new report on Sunday that it has gathered photographs, video and other evidence indicating that cluster munitions have been used in saudi airstrikes in Saada province, in Yemen's northern mountains.
Photographs published by the monitor show two large aluminium shells discovered in the al-Safraa district of Saada province on 17 April, just over three weeks into the Saudi-led bombing campaign, Middle East Eye reports.
HRW said that analysis of satellite imagery suggested the weapons had landed on a cultivated plateau, within 600 metres of populated areas.
According to the group, evidence indicates that multiple attacks may have been carried out.
Cluster munitions are prohibited by a 2008 treaty adopted by 116 countries, but not by Saudi Arabia and its coalition partners or the United States.
"Saudi-led cluster munition air strikes have been hitting areas near villages, putting local people in danger,” said HRW arms director Steve Goose.
"Saudi Arabia and other coalition members – and the supplier, the US - are flouting the global standard that rejects cluster munitions because of their long-term threat to civilians."
The BLU-108, which is also sold to the UAE, is banned by the Convention on Cluster Munitions.
A Yemeni man receives treatment at a hospital in the south-western province of Taiz (AFP)
On Friday a series of airstrikes in south-western Yemen hit a hospital and a medical camp killed at least 58 civilians, many of them medical staff and patients, according to local officials.
Saudi Arabia recently became the world’s biggest arms importer – one of its largest suppliers is the US, which sold over $5.5 bn in weapons to the Gpersiam Gulf heavyweight in 2013.
US arms sales to its regional ally are now at an all-time high, after jumping by over 100 percent between 2012 and 2013. Figures for 2014 have not yet been made available.