Syrian opposition leaders have called for air strikes against the Islamic State group [Reuters]

Islamic State Group 'Executes 700' In Syria -- Al Jazeera

Activists say the killings of Sheitat tribesmen, many by beheading, happened over the last two weeks.

The Islamic State group has executed 700 members of a tribe it has been battling in eastern Syria during the past two weeks, the majority of them civilians, a monitoring group said.

The killing spree happened in several villages inhabited by the al-Sheitat tribe in Deir Ezzor province, where the tribe are from, the Syrian Observatory for Human Rights said on Saturday.

The Observatory said many of the victims, who were Sheitat tribesmen, were beheaded after they were captured by the Islamic State group.

Among the members of the Sheitat tribe killed were 100 fighters, but the rest were civilians, the activist group, which opposes Syrian President Bashar al-Assad, said.

Read more ....

Update #1: Islamic State fighters massacre as many as 700 Syrian tribesmen, activists report -- AP
Update #2: Islamic State executes 700 members of Syrian tribe, mostly civilians - report -- RT

My Comment: There are few (if any) outside international observers within the Islamic State .... so confirmation of these reports is always hard to be found. But the accounts from refugees who are fleeing from territory that is controlled by the Islamic State are universal in describing the sheer terror that grips their communities once these fanatics have established and consolidated their rule.