US-backed militias said they captured a major oil field in Deir al-Zor province on Sunday, pressing their offensive against Islamic State fighters in eastern Syria.
The Syrian Democratic Forces (SDF) said they gained control of al-Omar oil field, one of Syria's largest, on the eastern bank of the Euphrates river.
With air strikes and Special Forces from the US-led coalition, the SDF has been battling Islamic State in oil-rich Deir al-Zor, bordering Iraq. The SDF alliance of Kurdish and Arab militias has been focused on territory east of the river, which bisects the province.
The Syrian army, with Russian air power and Iran-backed militias, has been waging its own separate offensive against Islamic State militants, mostly to the west of the river.
The US-led coalition and the Russian military have been holding de-confliction meetings - to prevent clashes between planes and troops - though the offensives have sometimes come into conflict.
Al-Omar oil field lies some 10 km (6.21 miles) north of the town of al-Mayadin, which government forces and their allies took earlier this month.