"This is really a big lie, which is laughable. We do not have chemical weapons and do not allow its application against anyone, and even more so against our civilians," Alloush, who also heads the Riyadh-backed High Negotiations Committee, said on the sidelines of the intra-Syria Geneva talks.
Instead, he once again accused Syrian President Bashar Assad of using chemical weapons in the country.
"[The information] that this type of weapon has been used [by Jaysh al-Islam] is absolutely wrong. What we used was Grad multiple rocket launchers, it is allowed, these rockets are simple, characterized by low weight and are considered to be defensive rather than offensive [rockets]," he added.