Syria's army and allied fighters have captured the city of Deir Ezzor from the Islamic State (ISIS) group in a Russian-backed operation, the Syrian Observatory for Human Rights said on Thursday, according to AFP.
There was no immediate confirmation from official sources, though state media earlier reported army advances in the city in the country's east.
"Regime forces and allied fighters... with Russian air support have full control of Deir Ezzor city," the Britain-based Observatory said.
"Fighting has ended, now there are sweeping operations under way," Observatory director Rami Abdel Rahman was quoted as having said.
Earlier, the Observatory and Syrian state media reported Syrian government troops had captured three new neighborhoods from the jihadists.
A military source said, however, the government only held around 80 percent of the city.
Syria's army broke into Deir Ezzor in September, ending an ISIS siege of nearly three years on government-held parts of the city.
ISIS once held most of Deir Ezzor province, an oil-rich region that runs along the eastern border with Iraq.
The group has come under attack from two separate campaigns, including the regime's Russian-backed assault, and another operation by the U.S.-backed Syrian Democratic Forces, an alliance of Kurdish and Arab fighters.
News of the capture of Deir Ezzor came several days after Russia said its submarine deployed in the Mediterranean fired three ballistic missiles to destroy an ISIS command post in Deir Ezzor province.
The submarines used by Russia are covered from Syria by Moscow’s S-300 and S-400 missiles systems and its Bastion coastal defense system.