Islamic State militants killed nearly 20 people including two children in a village in Syria's eastern Deir al-Zor province, and captured fighters participating in a US-backed operation against the jihadists, a monitoring group said on Saturday.
The British-based Syrian Observatory for Human Rights said the militants had raided the village of Jizrat al-Boushams, northwest of Deir al-Zor city and near the provincial boundary with Raqqa on Friday.
The Observatory posted a video showing the corpses of around a dozen men who had apparently been shot. Reuters could not verify the video's authenticity.
Islamic State withdrew from the village after the attack taking the captured fighters, it said.
The ultra-hardline group has staged attacks on villages near areas it controls as it is being pushed back towards its strongholds of Raqqa and Deir al-Zor.
Separate forces are fighting the Islamists, who are enemies of all other sides in the Syrian conflict, including US-backed Kurdish and Arab fighters, and Russian-backed Syrian forces.