The Syrian army said on Sunday it had captured a string of villages from US-backed Syrian Democratic Forces (SDF) east of the Euphrates river near the border with Iraq where Kurdish-led forces are in control, state television said.
The U.S.-backed proxy forces spearheaded by the Kurdish YPG militia since last year have taken over much of the territory east of the Euphrates in Deir al-Zor province as part of a major campaign that drove Islamic State militants from eastern Syria.
The Russian-backed Syrian army has rarely clashed with SDF forces in its campaign against Islamic State and had kept away from their areas east of the Euphrates, focusing on regaining territory from the militants west of the river.
SDF officials were not immediately available for comment.
There have been elaborate "deconfliction lines" separating the US-led coalition forces present on the eastern side of the river from the Russian and Iranian backed forces on the western side to prevent clashes, US army officials and defence analysts say.
Earlier on Sunday, the SDF said they were engaged in heavy clashes with Syrian army troops on the outskirts of the village of Janin near the Euphrates.
They accused the Syrian authorities of seeking to disrupt preparations by the US-led coalition to resume an imminent offensive against Islamic State in several pockets of territory along the middle Euphrates river that they still control.
In February US airstrikes killed and wounded hundreds of pro-government forces including Russian paramilitary contractors who were advancing near the eastern city of Deir al-Zor towards one of the largest gas fields in the hands of US-backed forces.