Western-backed Syrian rebels holding a strategic swathe of the desert southeast stretching to the Iraqi border said they came under major attack on Tuesday from government forces and allied Iranian-backed militias backed by Russian air power.
They said hundreds of troops with dozens of armored vehicles including tanks had surged into the Bir Qassab area some 75 km (45 miles) southeast of Damascus towards the Badia region that skirts the borders with Jordan and Iraq.
Bir Qassab straddles the route to the eastern suburbs of Damascus, near the Dumeir air base, that is also a key rebel supply line towards areas they control further southeast.
Bir Qassab fell to Free Syrian Army (FSA) rebels after it was abandoned a few months ago by Islamic State (IS) militants beating an eastward retreat to reinforce their urban bastion, Raqqa, against a U.S.-backed coalition offensive, and Deir al Zor province against a thrust by Syrian government forces.
Bir Qassab had given Islamic State a springboard for attacks on territory just to the east of Damascus and a base for maintaining their grip on large swathes of the Badia region.
“The (Syrian) regime and militia ground attack started this dawn and our forces are holding on to their positions,” said Saad al Haj, spokesman for Osoud al Sharqiya, one of the largest rebel groups operating in the area.
“With (the help of) intensive Russian bombing they are trying to advance but we are repelling them,” al-Haj added.
President Bashar al-Assad’s forces, aided by Iranian-backed militias, have engaged in a race with FSA rebels in recent weeks to seize areas in the southeastern desert vacated by retreating Islamic State insurgents.
The government offensive is part of a major campaign to recover control of territory south of the ancient central town of Palmyra, putting Assad’s forces within reach of the Iraqi frontier for the first time in years.
This move has also effectively encircled FSA-controlled desert territory stretching to the Jordanian and Iraqi borders and close to the Tanf garrison where U.S. forces are based.
Iranian-backed forces have also been trying to advance towards the base even after repeatedly being bombed by the U.S. led coalition.
U.S. forces said on Tuesday they had shot down an armed “pro-Syrian regime” drone near the garrison. A Western intelligence source identified the drone as Iranian.