The human rights organization Human Rights Watch published a report on the use of chemical weapons by the Syrian government army during the last month of fighting in Aleppo at the end of 2016.
According to human rights activists, between November 17 and December 12, the military used poisonous chlorine gas in rebel-controlled areas of Aleppo at least eight times. As a result, nine civilians were killed, including four children; about 200 people were injured.
The report states that there are reports of 12 chemical attacks, but the report includes those cases reported on social media in real time and later confirmed during interviews.
Human rights activists say it is difficult to pinpoint the gas used without laboratory analysis, but eyewitness accounts of the smell of the gas and symptoms of poisoning suggest that the military used chlorine. In four cases, eyewitnesses saw characteristic yellow or yellow-green smoke in moments, in two cases journalists filmed it.