ISIL is said to have kidnapped 400 civilians in an attack on a city in eastern Syria.
The families of pro-government fighters were among those seized as the fanatics moved in on parts of Deir al-Zour according to the opposition monitoring group, The Syrian Observatory for Human Rights.
It says some 135 people were killed in the assault. Syrian state media said at least 300 had died, including women and children. A source close to the government in Damascus said some of those killed had been beheaded.
Deir al-Zour province links ISIL’s de facto capital in Raqqa with territory controlled by the militant group in neighbouring Iraq.
As well as dropping bombs in a push to help Syrian President Assad defeat his opponents, Russia’s Air Force has been dropping humanitarian aid to those trapped in Deir al-Zour.
Unverified reports say some have already died of starvation there and the United Nations has warned that 200,000 residents face a severe food shortage and sharply deteriorating conditions.
Local aid workers have reported 32 deaths from starvation among another besieged population, some 42,000 people trapped in the Syrian town of Madaya.