On Monday, Ukraine accused Russia of intensifying frontline attacks using banned hazardous chemicals, including tear gas. This is the latest in a series of mutual allegations of war crimes and the use of prohibited chemical weapons by both sides in the ongoing conflict, now in its third year.

The Ukrainian military reported 715 instances of Russian forces using ammunition with “hazardous chemical compounds” in May, an increase of 271 cases from the previous month. It stated that Russian forces were primarily deploying these substances via grenades dropped by drones.

Medical facilities have recorded 1,385 visits from soldiers exhibiting “symptoms of chemical damage of varying severity.”

Ukraine claimed that Russian forces were using chemicals, mainly CS gas, which is typically used by law enforcement but is banned on the battlefield under the Chemical Weapons Convention (CWC), to which Russia is a signatory.