Dozens reported killed in Russian strikes in Deir Ezzor and Raqqa

At least 33 civilians were killed in air strikes suspected to have been carried out by Russian warplanes on a village in eastern Syria on Saturday, a monitoring group said.

The Syrian Observatory for Human Rights said seven children and one woman were among the dead in the village of Khasham in Syria's oil-rich Deir Ezzor province.

Controlled by the Islamic State (IS) militant group, Khasham lies just 20 kilometres southeast of the provincial capital, also called Deir Ezzor, most of which is now held by IS. 

The Observatory said the death toll was likely to rise as "dozens" more people were wounded.

The monitor relies on a network of activists on the ground and says it distinguishes between Syrian, Russian and US-led coalition aircraft based on flight patterns as well as the type of planes and ordnance used.

On Friday, air strikes killed at least 44 civilians in Tabiyyah Jazeera, a village adjacent to Khasham. It was unclear if those raids were carried out by Russian or Syrian government warplanes.

IS has besieged most of the remaining government-held areas of the city since last March.

The latest air strikes come as Syria's government pushes to retake territory captured by IS after an offensive by the militant group on 16 January. 

The multi-front assault on Deir Ezzor and subsequent fighting has left nearly 500 people dead, according to the Observatory. 

While IS holds most of the province, the government has clung onto parts of the provincial capital as well as the nearby military airport.

The group has also tightened its siege of the roughly 200,000 people still living inside the city. 

In Raqqa city, Islamic State's de facto capital in Syria, at least 32 people were killed on Friday, the observatory said.

Russia, a staunch ally of President Bashar al-Assad's government, began an air campaign in support of Damascus in September.

The Observatory earlier this week claimed that Russian airstrikes have killed more than 1,000 civilians since September, including more than 200 children.

Meanwhile, according to Syrian military and security sources, US special forces and experts are setting up an airbase in northeast Syria as part of the battle against the Islamic State.

The sources told AFP that work was underway to expand an airfield in Rmeilan, in Hasakeh province.

A Syrian military source said nearly 100 "American experts," alongside forces from the anti-IS Kurdish People's Protection Units, had widened the landing strip and refurbished some infrastructure. 

"The airbase will be used for helicopters and cargo planes. Its strip is now 2,700 metres long and is ready to be used by planes that will transport equipment and ammunition," the source said. 

On Friday, the US denied that it had taken control of the airfield, according to an Al Jazeera report.