The Russian military says it has evidence of the use of chemical weapons by rebels in Syria's besieged city of Aleppo.
"Experts from the Russian Defense Ministry have found unexploded artillery ammunition belonging to terrorists that contains toxic substances," the military said in a statement on November 11.
According to the statement, the toxic substances in the rebels' ammunition are very likely to be chlorine gas and white phosphorous.
Using chlorine as a weapon is banned under the Chemical Weapons Convention, which Syria joined in 2013 under pressure from its ally Russia.
Russia's Defense Ministry said a more thorough analysis will be carried out by a Russian military lab.
Last month, the Organization for the Prohibition of Chemical Weapons concluded that Syrian government forces carried out three chlorine gas attacks on villages in 2014 and 2015.
Russia, however, has dismissed the findings as "unconvincing" and said no sanctions should be imposed on Syria for the chlorine gas attacks.