The world's chemical weapons watchdog on Monday said it had found traces of tear gas in samples taken last month on the frontline with Russia in Ukraine's central-east Dnipropetrovsk region.
The use of riot control agents such as tear gas as a method of warfare is prohibited under the Chemical Weapons Convention, the non-proliferation treaty overseen by the Organisation for the Prohibition of Chemical Weapons (OPCW).
Ukraine had requested the assistance of the agency, which deployed a team. The team was not mandated to assign blame, but Ukraine and the United States have said Russia has illegally deployed tear gas to clear trenches.
Tear gas is not lethal, but causes temporary irritation to the eyes and respiratory system.
OPCW's team reviewed digital files, received first-hand witness accounts, and tested three samples from a trench along the frontline with Russian troops, it said in an executive summary.
Analysis of samples conducted by two independent laboratories indicates that "both the grenade collected from the trench and the soil sample collected from the dark splatter next to it contained the riot control agent 2-chlorobenzylidenemalononitrile, known as CS", it said.
The findings are expected to be discussed at a meeting of the OPCW's 193 member states in The Hague next week.
