At least 10 Syrian soldiers were killed in fighting Tuesday with Islamic State jihadists in the eastern province of Deir Ezzor that also took the lives of three civilians, a monitor said.
The Syrian Observatory for Human Rights said the fighting was in Hawijat Sakr on the Euphrates River, not far from Deir Ezzor military airport, a key remaining post for the Syrian army in the oil-rich province.
The Islamic State group controls the majority of the province, but parts of the regional capital, Deir Ezzor city, are still in government hands, along with the airport.
Deir Ezzor has been a key target of strikes against IS by the US-led coalition fighting the jihadist group in Syria and Iraq.
When the raids began, IS withdrew from several positions, and there have been few reports of clashes involving the group in the province since.
Elsewhere in Syria, the Britain-based Observatory reported at least 12 people killed, including three children, in regime air strikes on the Ain Tarma area outside Damascus.
Ain Tarma is under rebel control and is one of the areas around the capital that regime forces have been battling to recapture.
Although government forces control Damascus, rebels often fire missiles into the city from several strongholds on its outskirts.
On Tuesday, the regime also carried out air strikes against Irbin, another rebel-held area east of Damascus, the Observatory said.
The strikes killed eight people, although the group said the toll was likely to rise because several of the wounded were in serious condition.