The Islamic State militant group has killed 1,878 people in Syria during the past six months, the majority of them civilians, a British-based Syrian monitoring organization said on Sunday.
Islamic State militants also killed 120 of its own members, most of them foreign fighters trying to return home, in the past two months, according to the Syrian Observatory for Human Rights.
The militant group has taken vast parts of Iraq and Syria and declared a caliphate in territory under its control in June. Since then it has fought the Syrian and Iraqi governments, other insurgents and Kurdish forces.
Rami Abdulrahman, the head of the Syrian monitoring group, told Reuters that Islamic State fighters killed 1,175 civilians, including eight women and four children.
He said 930 of the civilians were members of the Sheitaat, a Sunni Muslim tribe from eastern Syria that fought the Islamic State group for control of two oilfields in August.
Reuters cannot independently verify the figures, but the Islamic State group has publicized beheadings and stoning of many people in areas it controls in Syria and Iraq. These are for actions it sees as violating its reading of Islamic law, such as adultery, homosexuality, stealing and blasphemy.
The group, an offshoot of al-Qaida, has also released videos of executions of captured enemy fighters, activists and journalists.
