A US-backed force battling the Islamic State group in eastern Syria said six of its fighters were wounded on Saturday in air strikes by regime and Russian warplanes.

It is the first time the Syrian Democratic Forces, an alliance of Arab and Kurdish fighters, have said they have been hit by Russia.

The SDF and Russian-backed Syrian government forces are conducting parallel but separate offensives against IS in the eastern province of Deir Ezzor.

"At 3:30 am (0030 GMT) on September 16, 2017, our forces east of the Euphrates River were targeted by Russian and Syrian regime warplanes in the Al-Sinaaiya area," the SDF said.

It said six of its fighters were wounded.

Al-Sinaaiya is an industrial area northeast of the city of Deir Ezzor, about seven kilometres (four miles) from the east bank of the Euphrates.

"At a time when the SDF's brave forces are scoring great victories against IS in Raqa and Deir Ezzor... some parties are trying to create obstacles to our progress," the statement said.

The SDF's assaults against IS in Deir Ezzor and in Raqa further up the Euphrates Valley are both backed by the US-led coalition.

The Syrian government's offensive in Deir Ezzor is backed by Russia.

The SDF says it not coordinating its operations with the government or Russia.

But the coalition says there is a de-confliction line to prevent the two offensives from clashing.

Source: AFP