BEIRUT: Russian-backed Syrian troops pushed into the Islamic State group's bastion province Raqa today, threatening to catch the jihadists in a pincer movement as US-backed Kurdish-led fighters advance from the north.
The lightning advance from the southwest with Russian air support brought the army to within 40 kilometres of the Euphrates Valley town of Tabqa, site of the country's biggest dam, the Syrian Observatory of Human Rights said.
The dam, 40 kilometres upstream from the jihadists' de facto Syrian capital Raqa city, is also the target of the Washington-backed offensive which Kurdish-led fighters launched late last month.
It was the first time that government troops had entered Raqa province since they were ousted by IS fighters in August 2014.
Regular army troops were backed by militia newly trained by the regime's ally Russia, Observatory director Rami Abdel Rahman told AFP.
He said that the twin offensives which threaten to cut off IS-held Raqa from jihadist-held territory along the Turkish border raised suspicions that Moscow and Washington were covertly coordinating operations by their respective Syrian allies.
"It seems there has been an undeclared coordination between Washington and Moscow," he said.
At least 26 jihadists and nine government troops and militia were killed in the army's advance, according to the Britain-based Observatory, which relies on reports from medics and activists on the ground.
Tabqa dam has a huge reservoir named Lake Assad after President Bashar al-Assad's late father and predecessor Hafez.
When IS overran the area with its garrison and airbase in 2014, it summarily executed 160 captured regime troops.
The jihadists are facing counter-attacks on multiple fronts.
Arab and Kurdish fighters backed by Washington have launched an assault on the strategic Manbij pocket further up the Euphrates on the Turkish border, regarded as a key entry point for foreign jihadists.
Hundreds of kilometres downstream in neighbouring Iraq, elite Iraq troops have launched an assault on the emblematic IS bastion of Fallujah.
Washington has deployed more than 200 special forces troops in support of the Kurdish-led Syrian Democratic Forces, which it regards as the most effective fighting force on the ground against IS in Syria.
The SDF controls a large swathe of northeastern Syria along the Turkish border and another border enclave in the northwest.
The SDF's offensive against the Manbij pocket is aimed at seizing the last stretch of border still under IS control and denying the jihadists any opportunity to smuggle in recruits and funds.
The US military said the assault had captured more than 100 square kilometres of territory from IS this week.