Reports say hundreds of foreign-backed militants including a 1000-strong brigade from the so-called Sham Army have defected to the notorious group in recent days.
The defectors travelled from their base in the northwestern Syrian province of Idlib to the ISIL stronghold city of Raqqa last weekend.
In addition, several brigades affiliated with the Western-sponsored Free Syrian Army have pledged allegiance to ISIL in the east of the country.
The defections raise questions about the US military support for groups it classifies as moderate militants.
On July 8, the Saudi daily Akkaz confirmed in a report that the foreign-backed militants have received the second batch of US-made anti-tank missiles.
The Takfiri militants have reportedly received TOW anti-tank rockets in the strategic Qalamoun region.
Comment: The US is funding and arming terrorists! Can it be any clearer?
Comment: The US is the master of chaos and destruction.