isis execution
A man purported to be Islamic State captive Jordanian pilot Muath al-Kasaesbeh stands in front of armed men in this image released on Feb. 3, 2015. He was murdered by the group. Reuters/Social media via Reuters TV

Since the establishment of its self-proclaimed caliphate in parts of northern Iraq and Syria in June last year, the Islamic State group has executed over 2,150 people in Syria alone, the Syrian Observatory for Human Rights said, in a statement released Tuesday. This number includes over 1,300 civilians and nearly 530 Syrian government troops.

“We believe that the real number of people that have been killed by IS is higher than the number documented by SOHR because there are hundreds of missing and detainees inside IS jails, and because there are dozens of Kurds who are still been missing since the beginning of IS attack on the countryside of Kobani in September 16,” the U.K.-based organization said, in the statement.

Moreover, this number does not include the killings in ISIS-held territories in Iraq, and the recent spate of executions of Ethiopian Christians in Libya. However, even if the Observatory’s estimate is taken as an exact figure, it adds up to 215 executions every month, or an average of seven executions daily over the last 10 months.

“Charges have ranged from insulting God (blasphemy), spying for the benefit of the Nusayri [Alawite] regime, sodomy and dealing and supporting YPG [Kurdish forces],” the Observatory said, in the statement.

Several members of local Sunni tribes, such as the al-Sheitaat, have also been victims of mass killings. In August last year, ISIS allegedly executed 700 members of this tribe in eastern Syria, after they fought to prevent the advance of the militant group.

The latest estimate comes just days after a video showing the execution of two blindfolded men, accused of being gay, emerged online. While these two men were stoned to death, previous videos have shown people being thrown off roofs, crucified, shot or beheaded for the same "crime."

It is not yet clear whether the latest estimate includes the beheadings of Western hostages on camera by ISIS executioner “Jihadi John” -- identified as a 26-year-old Londoner named Mohammed Emwazi.