The provincial city of Deir al-Zour has been devestated by recent years of fighting, most recently with the deaths of displaced civilians staying in camps on the western bank of the Euphrates River, according to activists. 

The BBC states that it was not possible to verify the reports, with no comment from Russian sources. 

However, Russia is confirmed to be providing air cover to Assad-regime forces battling Daesh in the Euphrates valley. 

Last week, Daesh's long-running siege of a government-held enclave in Deir al-Zour and a nearby military airport was broken.

Assad forces are now seeking to advance southwards, on the western side of the Euphrates towards the town of Abu Kamal, along the border with Iraq.

Meanwhile, a US-backed alliance of Kurdish and Arab fighters - the Syrian Democratic Forces, has launched a separate offensive in the same direction on the eastern bank.

The Syrian Observatory of Human Rights reported that at least 69 people had been killed in suspected Russian strikes in the past three days.