DAMASCUS - The Syrian army on Thursday entered Albu Kamal, the last town in the country held by the Islamic State group, several days after the jihadists recaptured it, a monitor said.
The town in the eastern province of Deir Ezzor on the border with Iraq was initially captured by the army and allied forces a month ago but IS retook it in a counterattack.
The Britain-based Syrian Observatory for Human Rights said the new offensive had successfully penetrated the town, with troops backed by Russian air strikes advancing from the west, east and south.
"Fighting is ongoing inside the town, there is artillery fire and there are Russian air strikes," Observatory director Rami Abdel Rahman said.
The first assault on Albu Kamal was spearheaded by Syrian government allies, including Iraqi and Lebanese Shiite fighters, and advisers from Iran's Revolutionary Guard, the Observatory said.
"This time, the military operation is being led directly by regime forces," Abdel Rahman said, adding that troops had taken the town's eastern, southern and western suburbs.
IS still holds around 25 percent of the countryside of Deir Ezzor province but are under attack not only by government forces but also by US-backed Kurdish-led fighters.
The jihadists once controlled a territory the size of Britain, proclaiming a "caliphate" in 2014 that spanned Syria and Iraq.
But they have successively lost all their key strongholds, including Raqa in Syria and Mosul in Iraq.