ISIS forces attack Syrian army with mustard gas, sources say

Syrian military sources and Western sources monitoring the war in Syria reported Tuesday that ISIS forces in the area of Deir al-Zor fired missiles with mustard gas warheads at besieged Syrian forces.
None of the sources specified the number of casualties in the attack in eastern Syria near the Iraqi border.
DEBKAfile sources: ISIS has been trying to capture the Syrian military bases in Deir al-Zor, especially the air force base, for more than six months but all of the attacks until now have failed.