Heavy fighting has been reported in a suburb of Damascus as government forces loyal to Syrian President Bashar al-Assad try to wrest the area from control of rebel fighters.

The suburb of Jobar on Saturday was the scene of some of the heaviest fighting the rebels holding the area have seen in the past year, they told Al Jazeera.

It comes as a prominent Syrian activist group monitoring the civil war said US-led air strikes in the country have killed more than 900 people since September.

Both fighters belonging to the Islamic State of Iraq and the Levant (ISIL) and civilians were included among the dead, the UK-based Syrian Observatory for Human Rights said.

The activist network said air strikes have killed 785 ISIL fighters, as well as 72 members of al-Nusra Front, an affiliate of al-Qaeda based in Syria.

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The group also said strikes have killed 52 civilians, including eight women and five children.

Coalition air strikes targeted oil refineries and oil fields in Deir Az Zor, Hasakah and Raqqa.

The Syrian Observatory strongly condemned the deaths of the civilians caught up in the strikes, and renewed calls to neutralise civilian areas of the country as a means of preventing military operations from either side.

A US-led coalition began striking ISIL in late September in Syria after targeting the group in Iraq.

The operation could be a guise for trying to "surreptitiously" topple Bashar al-Assad's regime, Russia's foreign minister said on Saturday.

The comments by Sergey Lavrov came in advance of planned talks in Moscow between Russian President Vladimir Putin and a Syrian delegation.

"Possibly ... this is not so much an operation against Islamic State as the preparation for an operation to change the regime surreptitiously under the cover of this anti-terrorist operation," he told a forum of politics experts in the Russian capital, quoted by TASS news agency.

Lavrov accused the US of having "perverted logic" over Assad, saying it blamed the Syrian president for the flood of fighters arriving in the region.

"The Americans say that Assad's regime is a very important factor that brings terrorists to the region to try to topple him. I think this is absolutely perverted logic," Lavrov said.

Russia has been a staunch ally of Assad's regime throughout Syria's civil war and has repeatedly thwarted UN action against him.

Source: Al Jazeera and agencies