SDF says it was attacked at gas field in Deir Ezzor province
US-backed Syrian militias said Russian warplanes struck their positions in Deir Ezzor province on Monday, near a major natural gas field they seized from Islamic State in recent days.
"Russian air strikes and mortar fire hit the Conoco gas plant where a large number of our forces are stationed, and the preliminary toll is at least six wounded," said Syrian Democratic Forces spokeswoman Lilwa Abdallah.
She said Syrian government forces carried out additional bombardment of SDF positions after the initial Russian bombing.
"We reserve the right to respond," added Abdallah.
Spokesman Mustafa Bali said the attack on Monday "by land and air" had wounded SDF fighters.
The Russian defence ministry denied the SDF's claims, saying it was always careful to ensure its air strikes were accurate, the RIA news agency reported.
The SDF, an alliance of Kurdish and Arab militias, has been fighting Islamic State on the eastern bank of the Euphrates river with US-led jets and special forces.
The SDF and Syrian troops with Russian air power have converged on IS in separate offensives in Deir Ezzor.
A "de-confliction" line is supposed to prevent the two campaigns from clashing, but Monday's alleged bombardment is the second time the SDF has accused Russia and the Syrian government of hitting its fighters.
On 16 September, the group said six of its fighters were wounded in air strikes by government and Russian warplanes in the al-Sinaaiya area around seven kilometres from the eastern bank of the Euphrates.