Syria’s Army broke a years-long Islamic State (IS) group siege on the government enclave of Deir Ezzor city on Tuesday as it battles to expel the jihadists from a key stronghold.

The jihadist group has already lost more than half of its nearby bastion of Raqqa to U.S.-backed forces, and the loss of Deir Ezzor city and the surrounding oil-rich province of the same name would leave it with only a handful of isolated outposts.

Russian air support

Syria’s Army and allied fighters, backed by Russian air support, have been advancing towards Deir Ezzor on several fronts in recent weeks, and on Tuesday arrived inside the Brigade 137 base on its western edge.

“The Syrian Arab Army this afternoon broke the siege on Deir Ezzor city after its advancing forces arrived from the western province to Brigade 137,” state news agency SANA said. “This great achievement is a strategic shift in the war on terror and confirms the ability of the Syrian Arab Army and its allies,” the Army command said. A local journalist contributing to AFP on the ground said a minesweeper moved ahead of troops as they arrived at the base.

As they reached the soldiers who have been besieged inside the base and adjacent parts of the city, the troops embraced and shouted patriotic slogans. Others fired in the air and flashed victory signs, as Syrian and Russian warplanes flew overhead.

Syria's President Bashar al-Assad congratulated troops in a call to commanders at the base, his office said. “Today you stood side-by-side with your comrades who came to your rescue and fought the hardest battles to break the siege on the city,” he said.