Islamic State has been pushed out of the last major city where it had a presence, as the group loses further ground in Syria and Iraq.
After months of fighting, the army has regained “full control” of the eastern city of Deir el Zor on Friday, Syrian state television said.
Soldiers were now working to clear mines and other explosives from the areas captured from IS, the report said.
The Syrian forces victory comes after Islamic State in October was also pushed out of Raqqa, the Syrian city that served as de-facto capital of the group’s “caliphate”.
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The group has seen its territory shrink in recent months as the militants are driven out of the final areas they control in both Syria and Iraq.
IS seized control of much Deir el Zor and the surrounding oil-rich province in 2014, but never controlled the entire city.
Syrian forces have been fighting IS in the city since September, when they broke a nearly three-year IS siege on government-held areas.
The battle has left much of the city in ruins after being hit by Russian air strikes and heavy Syrian artillery fire.
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Reports from inside the city say entire floors of buildings have been destroyed and fallen onto those beneath.
On other buildings exterior walls have been totally blown off revealing the destroyed interiors.
The Syrian forces victory will be the latest blow to Islamic State, which at one point controlled vast swathes of Syria and Iraq.
They still control 35% of the Deir el Zor province, much of which is empty desert, as well as some areas of nearby western Iraq.
The Syrian forces victory in Deir el Zor took place as Iraqi troops also advanced against the militants over the border.
There Iraqi forces have entered al Qaim, in one of the last remaining areas held by IS in the country.
They are attempting to recapture the two towns of al Qaim and Rawa, in the Syrian border area.
Just hours after entering al Qaim, Iraq’s security forces retook a border crossing with Syria from the militants, according to the Joint Operations Command.
The US-led international military coalition, estimates that around 1,500 Islamic State fighters still remain in the immediate area around al Qaim.
The latest push comes after Islamic State lost control of Mosul in July and the town of Hawija in October.