Some 11,000 civilians and soldiers have been executed by the Islamic State since the jihadist group established a self-proclaimed caliphate last year, the Syrian Observatory for Human Rights (SOHR) said.

Of the figure, SOHR said 3,207 were put to death in Syria, while another 7,700 were killed in Iraq.

The casualties would be higher if those killed in war by the ISIS—including women and children—were included, the Christian Post said.

In killing people, according to the SOHR report, the group based its action on an ''extremist interpretation" of Shariah law using various execution methods such as beheading, shooting, drowning, stoning to death and throwing civilians and soldiers off buildings.

SOHR said many of the victims were killed for their faith; others for their sexuality and for being foreign nationals such as Americans.

"Christians and other minorities had been forced to choose between converting to Islam, paying heavy taxes and agreeing to other harsh conditions, or facing death,'' it said. Just recently, a 15-year old-boy was reported killed by the ISIS for being gay. Foreign nationals, on the other hand, had been put to death as ''a warning to the West to stay out of the region."

The SOHR, which keeps track of the daily violence and battles across Syria, also found out that at least 98 women and 76 children were among the civilians executed by ISIS in the war-torn country.

The persecution watchdog group In Defence of Christians had previously lobbied elected officials on Capitol Hill to pass a resolution describing ISIS actions as "genocide.''

"Christians and other ethnic and religious minorities have been murdered, subjugated, forced to emigrate and suffered grievous bodily and psychological harm, including sexual enslavement and abuse, inflicted in a deliberate and calculated manner," the resolution said.

The ISIS had been distributing disturbing photos and videos through its social media affiliates, including a video footage released in July showing children being forced to kill 25 Syrian soldiers inside the Roman amphitheatre in Palmyra, the Christian Post said.

Several countries such as the United States and France have pledged their commitment to defeat the ISIS, and have been bombing ISIS camps in Syria and Iraq.