A militant group battling the Islamic State (IS) terrorists in Syria captured and slaughtered dozens of IS members on camera, a media report said on Wednesday.
Dressed in orange jumpsuits -- the attire usually worn by the IS's victims -- the Jaysh Al-Islam militants led 13 shackled IS jihadis to their deaths, the Daily Mail reported.
Jaysh Al-Islam calls itself the "Army of Islam" and reportedly commands as many as 25,000 loyal fighters following the merger of around 60 rebel factions inside Syria.
The IS's captured militants were forced to kneel as a commander announced: "Allah did not make a disease without appointing a remedy to it."
The fighters -- dressed entirely in black -- were given something to drink before each of their faces was clearly shown in the 19-minute video. They were then shot in the back of the head at point blank range with shotguns.
Jaysh Al-Islam said: "The most serious calamity for our jihad today is a group of people who grow at a time of division among Muslims.
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"This group claimed to be the mother state and made terror on other Muslims, shed their blood and looted their properties and dignities.
"They wreaked havoc on our people in liberated areas and cut the supply route of jihadis."
In April this year, Jaysh Al-Islam released a striking video showing 1,700 troops, a fleet of armoured tanks and special forces "soldiers" in an impressive military parade.
It operates in the war-ravaged Syrian capital of Damascus and their ongoing battle against President Bashar Al-Assad is reportedly funded by Saudi Arabia.
The Arab kingdom has sent millions of dollars to arm and train their fighters so they can defeat the Syrian regime and "increasingly powerful jihadi organisations", according to the Guardian.
The insurgent group was created in 2011 when Saudi Arabia allegedly engineered the merger of over 50 rebel factions after becoming increasingly alarmed at the rise of Al Qaeda and IS in Syria.
The Jaysh Al-Islam is the enemy of both these Islamist groups as well as the Al Qaeda-affiliated Nusra Front, but embraces independent rebel forces and "non-jihadi" units.