The Syrian Democratic Forces have seized Syria's largest gas field from Islamic State militants, a senior commander has said.

Ahmed Abu Khawla of the Syrian Democratic Forces said the Conoco gas field and plant came under full control of the group on Saturday morning, after days of fighting with the extremists.

"This is the first gas or oil field in the campaign which we have liberated," he said.

The UK based Syrian Observatory for human rights reported that fighting was ongoing around the gas fields, and that several wells had been set alight as of Friday.

If reports are true the field will be a major gain for the SDF, a group of Arab and Kurdish militias who this month have been engaged in an offensive to take the Deir al-Zor area.


The advance follows days of fighting near the Euphrates river in the province of Deir al-Zor where the Islamic State is facing an onslaught from two sides.

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As the SDF encroaches from the east, the Syrian army and its allies are tightening their grip to the west, already controlling the town of Deir al-Zor and edging toward rebel forces.

As the groups near each other they are threatening to cut IS territory in two.

But their proximity raises new anxieties even as it threatens the extremist group.

Though they have a common enemy in IS, the SDF and Assad's forces disagree on key areas and are backed by rival international powers.

The SDF are mostly comprised of Kurdish forces and include groups closely affiliated with the Syrian revolution, which has been brutally suppressed by Bashar al Assad since it began in 2011. They are backed by the United States.

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The Russian-backed government forces of Bashar al Assad have vowed to retake the whole of Syria.

Russia said on Thursday that if US-backed forces like the SDF threatened Syrian government troops, it would not hesitate to target them.