Chemical warfare (illustration)
Chemical warfare (illustration)IDF spokesman's unit

Syria has used sarin nerve gas for the first time since 2013, a senior Israeli official anonymously told the Telegraph Wednesday, on Islamic State (ISIS) jihadists outside Damascus. 

Syria agreed to rid itself of its chemical weapons stockpile under a 2013 agreement that followed a sarin gas attack on a Damascus suburb, although it was revealed the regime maintained its arsenal by hiding it from the inspectors. 

Since then, both mustard gas and chlorine gas have been said to have been used in attacks. The Organization for the Prohibition of Chemical Weapons (OPCW) has since found chlorine has been "systematically and repeatedly" used as a weapon; government and opposition forces have denied using chlorine and have accused each other of doing so. 

But sarin indicates yet a greater step in flouting the international agreement; not only did a lethal sarin gas attack prompt the chemical weapons ban, after it killed 1,400 people outside Damascus, but it is far more lethal than chlorine gas. 

Syria conducted the sarin gas attack over three weeks ago, the Israeli official said, in an apparent aim to drive away ISIS from seizing two airbases northeast of the city.

ISIS suffered casualties so heavy that Jerusalem believes it was a sarin gas attack - and that Syrian President Bashar Assad saved the chemical from destruction because it was the deadliest weapon in his arsenal. 

“They deceived and they still have it [sarin],” the official told the Telegraph. “Recently, they have decided to use it again. Once a taboo is broken, it becomes a standard weapon that you use. There are no red lines and it [sarin] becomes a standard kind of weapon.”