More than 18,000 people have been killed by Isis over the past two years, according to a UN report released on Tuesday.
Between May and October, 3,855 people were killed by the terrorist group in Iraq alone, a 15 per cent increase on the numbers from December to April.
The report also found that Isis had by last summer enslaved an estimated 3,500 people in Iraq, mostly from the minority Yazidi community, and including hundreds of children.
Isis was continuing to murder innocent men, women and children, but was also increasingly killing suspects among its own fighters.
It has started executing a lot of its own people, whether because they are fleeing from the front line or are suspected of other things. And its abduction of children does make it look as if it is desperate to have enough fighters.
The report detailed Isis executions by shooting, beheading, bulldozing, burning alive and throwing people off buildings. Doctors, teachers and journalists opposed to its ideology have been "singled out and murdered".
The jihadist group reserved particular cruelty for those it viewed as assisting the Iraqi government.
In June, Isis claimed to have murdered 16 men in three batches - by a rocket-propelled grenade fired at a car in which some men were placed, by placing others in a cage that was submerged into water and by decapitating the remainder with explosives. The UN report said that the men had been accused of co-operating with the Iraqi army.
The true number of Isis fighters killed by their own group is difficult to determine. So too is the real number of civilian casualties, which is likely to be far higher than UN estimates.