Syria’s state-run television network reported that army and allied forces had advanced on the Brigade 137 base front on the western outskirts of the city, located 450 kilometers (280 miles) northeast of the capital Damascus on the shores of the Euphrates River, on Tuesday.

The move effectively breached the siege that Isis militants had laid since January 2015.

Meanwhile, the so-called Syrian Observatory for Human Rights (SOHR) said government forces are dismantling mines around the Brigade 137 base.

The Britain-based monitoring group added that Isis Takfiris are launching counterattacks in the area.

There are reports that fierce skirmishes are underway near the village of Jabra.

Earlier on Tuesday, Russia's Defense Ministry announced in a statement that one of its frigates in the Mediterranean had fired a salvo of Kalibr cruise missiles at a gathering of Isis militants near Deir ezzor.

Syrian leader congratulates army on breaking Deir ezzor siege

Meanwhile, Syrian President Bashar al-Assad has extended his congratulations to government troops on breaking the  Isis siege on Deir ezzor.

Assad, in a telephone conversation with Major General Rafiq Shehadeh, the head of the security committee in Deir ezzor, General Hassan Mohammed, the commander of the 17th Brigade, and Brigadier General Essam Zahruddin, the commander of the 104th Brigade in the Republican Guard, praised army soldiers for their sacrifice, self-devotion and great sense of responsibility to fulfill their duties and protect defenseless civilians against Takfiri groups.

“You will be a positive role model for generations to come. History will never forget that you sacrificed all you could, and managed to fully perform your duties without any fear or hesitation".

Syrian President Bashar al-Assad (Photo by AFP)

“History will remember that your comrades sacrificed their lives and were martyred for the sake of their homeland. Some continued the battle despite the wounds they had sustained. This pure blood produced a glorious victory over Takfiri terrorists, who are being supported regionally and internationally".

“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, and join you in the front line to clear the entire region of the menace of terrorism and restore nationwide security and safety.”

Syrian troops and allied volunteer fighters had been advancing for months toward Deir ezzor, the provincial capital city of the oil-rich province of the same name. Government forces are besieged in a handful of neighborhoods and a nearby airport.

On Monday, Syrian state media reported that the army had regained full control over the town of Kabajeb southwest of Deir ezzor.

Isis militants overran large parts of Deir ezzor Province, including its many oil fields, in mid-2014 as it seized areas in Syria and neighboring Iraq.

By early 2015, the Takfiri terrorists were in control of parts of Deir ezzor city, and besieged the remaining parts of it under government control.

It is estimated that 100,000 people remain in government-held parts of the city.

The SOHR estimates that more than 10,000 people may live in the Isis-held parts of the city.