At least 63 people, including nine children, have died in air strikes believed to be carried out by Russian warplanes on a town in eastern Syria, an independent monitor group has said.  

The Syrian Observatory for Human Rights said the raids on Khasham near the city of Deir al-Zor yesterday were among a series of strikes that also hit two other towns in the past 48 hours, killing scores of people.

Russian jets have been bombing around Deir al-Zor as Syrian pro-government forces clash with self-styled Islamic State fighters, who control most of the province.

The group has besieged remaining government-held areas of the city since last March and last week launched new attacks.

Warplanes have also hit Islamic State's de facto capital of Raqqa over the past two days, killing at least 44 people in the city, the Observatory said, raising its toll from yesterday after many of the wounded died of their injuries.

Meanwhile it is reported Syrian pro-government forces recaptured the rebel-held town of Rabiya in the western coastal province of Latakia earlier.

The advance, with the backing of Russian air strikes, was directed partly by Russian officers, the Syrian Observatory for Human Rights and Syrian state television said. 

It paved the way for a push by pro-government forces right up to the Turkish border, the SOHR added. 

Russia intervened in Syria's civil war on the side of President Bashar al-Assad in September.