It is described as a chemical massacre, committed by Syrian regime forces, using sarin gas - also called nerve gas - against the residents of Eastern Ghouta and Moadamiyeh Al-Sham, where more than 1,450 people - including women and children - were killed on August 21, 2013.
The attack came three days after the arrival of a mission of international inspectors to Damascus, and several international and UN reports indicated that the Syrian regime was responsible for it.