The Islamic State released at least 270 out of 400 civilians the militant Islamist group captured since it recently began battling the regime of Syrian President Bashar al-Assad for the eastern city of Deir al-Zour.

According to the Britain-based Observatory, most of the released prisoners were children under 14, men over 55 and women.

ISIL is still holding 130 civilians, mostly teenage and adult men, for questioning.

GETTYMuslim clerics stated they disagreed with the methods

Scores of people on both sides have been killed with the massacre of civilians reported.

Elaborating in a second interview with AFP news agency, Abdel-Rahman said the remaining captives would be questioned, and "if IS sees that they have no ties to the Syrian government, they will take a religious course and will be released".

"IS" now controls 60 percent of Deir al-Zour, and has continued unabated with suicide attacks on government targets since the weekend.

Aymenn Jawad al-Tamimi, a scholar and fellow at the Middle East Forum, obtained documents containing the same statement, CNN Money reports.

"I am afraid of a massacre that will repeat itself over and over if Daesh invades our neighbourhood", Hamdo said by phone, using an Arabic acronym for IS. Meanwhile, the Syrian government maintains a stronghold at a military airport and parts of the city.

Its most recent offensive "is putting thousands of people in the line of fire", said Linda Tom, spokeswoman for the UN's Office for the Coordination of Humanitarian Affairs, or OCHA.

"The Russian operation conducted military operations only in the provinces of Latakia and Deir Ezzor in light of unfavourable weather conditions and to avoid risks for the civilian population", Russian news agencies quoted military spokesman Igor Konashenkov as saying.

In an update published just before the attacks, OCHA said landmines lined the roads leading out of Deir Ezzor and that a majority of inhabitants were surviving on bread and water.