A Syrian military source has announced the recapture of three neighbourhoods of Deir Az Zor after eliminating the last remnants of the Islamic State of Iraq and the Levant (ISIL) group from the eastern city.

The army units, in cooperation with supporting forces, simultaneously regained control over the city's al-Hamidya neighbourhood, the official SANA news agency said late on Thursday.

The source said that army units continued their operations against ISIL, also known as ISIS, on the southwestern outskirts of Deir Az Zor, inflicting heavy losses on the ranks of the fighters and their equipment.

SANA quoted the source as saying army's engineering units started sweeping operations to demine the newly secured neighbourhoods.

Earlier, army units tightened encircled ISIL fighters in al-Hamidiya, Sheikh Yasin, al-Hawiqa and al-Rashida neighbourhoods in Deir Az Zor, amid a collapse in their ranks, a SANA reporter said.

The reporter said the army units restored control over the Public Park, Nour Hospital after violent clashes with ISIL fighters.

Assad's campaign

Backed by Russian air raids, the forces of Syria's President Bashar al-Assad have waged a sustained campaign to retake areas in Deir Az Zor province.

Meanwhile, a US-led international coalition has provided air support to a Kurdish-Arab alliance, the Syrian Democratic Forces (SDF), also fighting ISIL in Deir Az Zor.

Thursday's developments came a day after the Syrian opposition attending the latest round of talks in Kazakhstan rejected Russia's call for a conference in the Russian Black Sea resort city of Sochi.

The "Syrian Congress on National Dialogue", proposed by Moscow during the two-day talks in Astana, was expected to discuss the reconciliation between all of the warring parties, political reform and discuss the proposed new Syrian constitution.

"This is a Russian deception," said Fateh Hassoun who headed the Syrian opposition military delegation to the seventh round of Astana talks to end six-year-old Syria war.

"We don't trust the Russians because they are part of the war and they are fighting on behalf of the regime on the ground."