Fierce clashes in Syria's Deir az-Zour kill 73 fighters

Heavy clashes between Syrian regime forces and the Islamic State group in Deir az-Zour city have killed at least 73 fighters in the last 24 hours, a monitor said on Sunday.

Pro-Assad forces control most of Deir az-Zour city - the capital of the province in the east of the country - and made further advances after responding to an IS attack that began on Saturday, the UK-based Syrian Observatory for Human Rights monitor said.

The monitor said the fierce fighting on Saturday killed at least 50 Islamic State fighters, as well as 23 Syrian soldiers and pro-regime militiamen.

Observatory Director Rami Abdel Rahman said regime forces had captured two neighbourhoods and the municipal stadium.

"IS is now encircled in an area between the city and the (Euphrates) River," Abdel Rahman said.

IS once held large sections of Deir az-Zour city, and for nearly three years laid siege to other parts of it that remained under regime control.

In early September, advancing regime forces broke the siege, and they have been working since to expel the jihadists from the rest of the city.

Abdel Rahman said the fighting that began on Saturday was the fiercest in the city since September, adding that clashes were continuing on Sunday, with regime ally Russia carrying out heavy air strikes in support of the army and allied fighters.

Deir az-Zour, Syria [click to enlarge]

Deir az-Zour, an oil-rich province that borders Iraq, was once a stronghold of IS, but the jihadi group faces twin assaults there from the regime and the US-backed Kurdish-Arab Syrian Democratic Forces.

IS have already been expelled from neighbouring Raqqa province, and are now confined to just a few pockets of territory in Deir az-Zour.

The Syrian conflict began when the Baath regime, in power since 1963 and led by Assad, responded with military force to peaceful protests demanding democratic reforms during the Arab Spring wave of uprisings, triggering an armed rebellion fueled by mass defections from the Syrian army.

Russia has been operating a bombing campaign in Syria since 2015, when it stepped in to support Assad's rule and tipped the conflict in his favour. Human rights monitors say that the raids have resulted in many civilian casualties.

The brutal tactics pursued mainly by the regime, which have included the use of chemical weapons, sieges, mass executions and torture against civilians have led to war crimes investigations.