Russian forces in Ukraine used banned cluster munitions against civilians in the besieged city of Mykolaiv at least three times, killing several civilians, the Human Rights Watch (HRW) reported on Thursday. The report comes less than a day after US President Joe Biden flatly called Russian President Vladimir Putin a war criminal.

The international NGO reported that Russian forces fired cluster munition rockets into densely populated residential areas of Mykolaiv on three separate occasions – March 7, 11, and 13. The attacks left dozens injured and damaged homes, vehicles, and property in the city, with the March 13 attack killing nine civilians who were in line at a cash machine.

HRW interviewed six witnesses to the attacks and analyzed dozens of images and videos posted by witnesses or shared by others on social media to confirm Russian involvement.

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“They show damage from the attacks, four dead bodies, and remnants of the weapons that were used, including of Uragan and Smerch cluster munition rockets, as well as remnants and unexploded 9N210 fragmentation submunitions,” wrote HRW in its report.

According to the HRW, cluster munitions “pose an immediate threat to civilians during conflict by randomly scattering submunitions or bomblets over a wide area. They continue to pose a threat post-conflict by leaving remnants, including submunitions that fail to explode upon impact becoming de facto landmines.”

“Given the inherently indiscriminate nature of cluster munitions and their foreseeable effects on civilians, their repeated use in Mykolaiv during these three days of attacks might amount to war crime,” the HRW said.

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In view of the threat cluster munitions pose to civilians, their use, production, transfer, and stockpiling is banned under the 2008 Convention on Cluster Munitions, which 123 states have joined till date.

Since the beginning of the Russian invasion of Ukraine, Kyiv has repeatedly accused Russian forces of war crimes, but Western leaders had largely stopped short of labelling attacks on civilians as war crimes until now.

Over the past few days, however, Russian attacks on Ukrainian civilians have seen increasing international condemnation, and several investigations into the alleged war crimes, including one at the International Court of Justice (ICJ), is underway.