Forces allied with Syria's interim government have intensified ground attacks in the past 24 hours in an attempt to take two dams in the east of the country from a US-backed Kurdish militia, sources said.
The offensive is supported by Hayat Tahrir Al Sham (HTS), the group seeking to spread its control over the whole of Syria after the downfall of former president Bashar Al Assad's decades-long regime last month. An official in the Syrian Democratic Forces (SDF), a mostly Kurdish militia founded in 2014 and heavily backed by the US, told The National on Thursday that the SDF launched a counter-offensive "on different lines", aimed at capturing areas controlled by Turkish-backed, HTS-aligned forces.
About 40 people, mostly fighters, have been killed in the violence, according to tallies on both sides.
The violence reveals the threat of the conflict in north-east Syria, a Kurdish-run fief that makes up about a quarter of the country's territory, including most of the Raqqa and Hasakah provinces, and large areas of the Deir Ezzor and Aleppo governorates. The tribal area, especially in the Euphrates valley, is Syria's breadbasket and the source of most of its oil and gas production. Oil output was 200,000 barrels a day before 2011, when the civil war broke out, but has fallen by 75 per cent since then. The area also contains the bulk of the US military presence in Syria.
Two major US rivals, Russia and Iran, had also carved out zones of control in Syria before Mr Al Assad's downfall, along with Turkey, the main winner in the immediate aftermath of his removal.
An uprising in the region took place after the downfall of Mr Al Assad on December 8 and the SDF lost large parts of territory to an offensive that has been supported on some battlefronts from the air by Turkey. "We mobilised our elite fighters," said the SDF official.
He said the SDF this week regained control of parts of the main east-west M4 motorway in the governorate of Aleppo. The group was advancing towards Ras Ain and Tel Abiad, on the border with Turkey, as well as Manbij, which it lost last month to HTS and other forces.
Forces comprising HTS and the Syrian National Army, a Turkish proxy, now aim to take Tishreen Dam on the Euphrates. Another force mainly comprising Arab fighters who defected from the SDF last month, is attacking the SDF-held Tabqa Dam to the south.
Tabqa is not only the largest dam in Syria but also its single biggest source of electricity. Together with Tishreen, it lies off major roads dividing eastern and western Syria.
The expanded violence in the east comes after HTS leader Ahmad Al Shara met two US officials in Damascus on Tuesday. Syria's de facto leader held talks with State Department special envoy Nikolai Granger, whose brief is tied with the Kurdish fief in the east, and Daniel Rubinstein, from the department’s Middle East bureau.
"US officials again engaged the interim authorities in Damascus, and reaffirmed US support for inclusive and representative political transition," the department said after the meeting.
In Ankara, Turkey's military said it would continue operations in Syria if the SDF did not disarm. It also has to "respect the territorial integrity of Syria", the Turkish Defence Ministry said in a statement.
