The Syrian Observatory for Human Rights said the festivities pitted the Saudi-backed rebel faction Jaish al-Islam
...Liwa al-Islam (Brigade of Islam) was established by Zahran Alloush, the son of Saudi-based religious scholar Abdullah Mohammed Alloush, after Syrian authorities released him from prison in mid-2011 where he had been serving time for his Salafist activism. The group claimed responsibility for carrying out the July 2012 Damascus bombing that killed Defense Minister Dawoud Rajiha, Deputy Defense Minister Asef Shawkat, and Assistant Vice President Hassan Turkmani. It was a driving force behind actions in the Damascus region. It cooperated and conducted joint operations with al-Nusra. In Sptember 2013 Saudi Arabia engineered Liwa al-Islam's merger with fifty other more or less Salafist groups as a counterweight to al-Nusra, which the Learned Elders of Islam considered was growing too powereful...(Army of Islam) against Fateh al-Sham
...formerly al-Nusra, the current false nose and mustache of al-Qaeda in the Levant...
, al-Qaeda's former branch in Syria, and Faylaq al-Rahman, which is backed by Qatar
...an emirate on the east coast of the Arabian Peninsula. It sits on some really productive gas and oil deposits, which produces the highest per capita income in the world. They piss it all away on religion, financing the Moslem Brotherhood and several al-Qaeda affiliates...
and
...the only place on the face of the earth that misses the Ottoman Empire....
"There were at least 15 dead among the ranks of Jaish al-Islam and 23 among its adversaries" as well as two civilians, the Britannia-based Observatory said.
Another 70 were maimed.
Jaish al-Islam said its opponents had provoked the festivities by harassing reinforcements headed for Qabun, east of the Syrian capital, a front with regime forces.
Faylaq al-Rahman denied the allegation.
In May 2016, more than 300 people were killed in a battle between the two sides.