The Syrian Democratic Forces have been seizing territory from Islamic State with the support of US air strikes
The Syrian Democratic Forces said they captured a major oil field in Deir Ezzor province on Sunday, pressing their offensive against Islamic State fighters in eastern Syria.
The US-backed group said they took al-Omar field on the eastern bank of the Euphrates river in the early hours. "Our forces managed to liberate the fields without notable damage," said Lilwa al-Abdallah, spokeswoman for the offensive in Deir Ezzor province.
With the support of air strikes and special forces from their US allies, the SDF has been battling Islamic State in oil-rich Deir Ezzor, 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 fighters, mostly to the west of the river.
Deconfliciton meetings have been held by the US and Russian militaries to prevent accidental clashes between the two nations' forces, though the offensives have occasionally come into conflict.
Al-Omar oil field lies about 10km north of the town of al-Mayadin, which government troops and their allies took earlier this month. The town had turned into a major base for IS after the US-backed offensive drove them out of Raqqa.
The Syrian Observatory for Human Rights said IS fighters who had withdrawn from the oil field mounted a counter-attack overnight against government forces. The militants made some gains around al-Mayadin, the Britain-based monitor said.
A Syrian military source denied this, saying there was no significant attack and fighting raged on at the same pace.
Any attack by IS there was a "desperate attempt," the source said. "The Syrian Arab Army is attacking, hitting Daesh positions ... and advancing," the source said, using the Arabic acronym for Islamic State.
End of Islamic State 'in sight'
US President Donald Trump said on Saturday a transition can soon begin to set conditions for lasting peace in Syria now that the end of the Islamic State "caliphate is in sight" with the fall of their stronghold Raqqa.
The United States and its allies will support diplomatic negotiations "that end the violence, allow refugees to return safely home, and yield a political transition that honors the will of the Syrian people," Trump said in a statement.
The declaration came four days after US-backed Kurdish-led forces recaptured Raqqa, the capital of IS's self-proclaimed caliphate and its last major stronghold in Syria.
Trump said the entire city has been liberated from IS control, which he said marked a "critical breakthrough" in the global struggle against the militant group.
"With the liberation of ISIS's capital and the vast majority of its territory, the end of the ISIS caliphate is in sight," Trump said, using another acronym for the Islamic State group.
"We will soon transition into a new phase in which we will support local security forces, de-escalate violence across Syria, and advance the conditions for lasting peace, so that the terrorists cannot return to threaten our collective security again."