Nasser Haj Mansour 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. He added that SDF fighters also captured the nearby al-Izba gas field.
Another SDF spokesman, Brig. Gen. Talal Sillo, said the fighting in the area left 65 IS fighters dead while more than 100 gunmen surrendered. He added that IS had been controlling Conoco since 2014.
Sillo said that SDF fighters marched toward the field from the nearby village of Khsham under the cover of airstrikes by the U.S.-led coalition.
The Britain-based Syrian Observatory for Human Rights, which tracks the war in Syria with activists on the ground, reported later that SDF fighters took full control of the field in the province of Deir el-Zour. It said IS fighters are launching a counteroffensive to retake the field.
SDF fighters have been marching on the east bank of the Euphrates River in Deir el-Zour while Syrian troops are gaining in areas on the west bank of the river under the cover of Russian airstrikes. Earlier this week, Syrian troops crossed into parts of east bank but have concentrated their operations mostly on the west.
Deir el-Zour is a province rich in oil and gas and both sides have been racing to reach the fields. The next main target will be al-Omar oil field that is Syria's largest and is also on the east bank of the Euphrates, and Syrian government forces are also speeding to capture it. Oil revenues are badly needed for future reconstruction of Syria that has been plagued by war since 2011.
On Thursday, Russia warned against targeting its special forces in Deir el-Zour raising concerns over direct clashes between rival forces backed by Moscow and Washington fighting for the energy-wealthy region.
The warning was followed by an acknowledgement from the Pentagon of an unprecedented face-to-face meeting between Russian and American military leaders, which occurred inside or near Syria, to address the rising tensions.
Russia has been a main backer of Syrian President Bashar Assad and joined the war two years ago tipping the balance of power in his favor.
Elsewhere, In the northwestern province of Idlib, Russian airstrikes killed at least 20 people on Saturday, a day after a Russian submarine in the Mediterranean fired cruise missiles at insurgents in the province.
The Observatory said the airstrikes on the village of Tel Mardikh killed 28 members of the Failaq al-Sham insurgent group. It said that search operations for survivors under the rubble are still underway.
The Ibaa News Agency, the media arm of the al-Qaida-linked Levant Liberation Committee, said that more than 20 people were killed in the airstrike on the village without saying whether they were civilians or militants.
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