Syria's army battled the Islamic State group on the edges of Deir Ezzor Monday, seeking to break the siege of a government enclave and oust the jihadists from a key stronghold.

The jihadist group has already lost more than half of its nearby bastion of Raqa to attacking US-backed forces, and the loss of Deir Ezzor city and the surrounding oil-rich province would leave it with only a handful of isolated outposts.

Deir Ezzor province borders Iraq, where IS has also been expelled from former strongholds Mosul and Tal Afar.

The jihadists hold large parts of Deir Ezzor province, and more than half the provincial capital Deir Ezzor city, the remainder of which is controlled by the government and under IS siege.

Syrian troops backed by ally Russia have been advancing towards Deir Ezzor city on several fronts for weeks, and overnight they reached the Brigade 137 base on its western edge, a monitor said.

The Britain-based Syrian Observatory for Human Rights said Syrian troops outside and inside the base were battling to break the IS siege of the base.

"There have been multiple collapses of the Daesh (IS) line in western Deir Ezzor province, allowing the army to move quickly and arrive 10 kilometres (six miles) from the besieged forces," a military source told AFP. "The siege on the government troops will be broken within hours," he added.Syrian state media also reported the army was advancing towards the besieged base, which is adjacent to parts of the city still under government control.

Provincial governor Mohamed Ibrahim Samra, quoted by state news agency SANA, said besieged residents were already celebrating as the army neared.

"Yesterday Deir Ezzor city saw celebrations and rejoicing among all segments of society ahead of the expected victory with the advance of the Syrian Arab Army to the outskirts of the besieged city," he said.

IS seized large parts of Deir Ezzor province, including its many oilfields, in mid-2014 as it rampaged across Syria and Iraq.

By early 2015 it had also seized parts of Deir Ezzor city and laid siege to the remaining parts of it under government control.

The siege tightened further earlier this year, when IS advanced and cut the government-held parts of the city in two, with a southern section by the key military airport now divided from a northern sector.

An estimated 100,000 people remain in government-held parts of the city, which had a pre-war population of some 300,000.

The Observatory estimates more than 10,000 people may live in the parts of the city held by IS, although precise information is hard to come by.

Humanitarian crisis 

The siege has created a humanitarian crisis in the city, with food and medical shortages and soaring prices.

The government has brought supplies in by helicopter, and the United Nations has periodically airdropped humanitarian aid, but the situation remains difficult for those under siege.

Conditions are also reportedly dire for civilians trapped in IS-held parts of the city, with activists also reporting food and medical shortages as well as water and electricity cuts.

Syria's army has been advancing towards Deir Ezzor on several fronts in recent weeks, including from the west through neighbouring Raqa province, and from the south via central Homs.

Observatory director Rami Abdel Rahman said forces advancing from the southwest were now less than 20 kilometres (12 miles) from the key Deir Ezzor military airport and are also advancing from the north towards the city.

Capturing Deir Ezzor would be a key gain for Syria's government, which has scored a series of military victories in recent months with Russian support.

It has moved quickly towards the city, seeking to head off potential rival advances by US-backed fighters including the Kurdish-Arab Syrian Democratic Forces alliance which is conducting a separate battle to oust IS from the city of Raqa.

More than 330,00 people have been killed in Syria since the conflict began with anti-government protests in March 2011, before spiralling into a multi-front civil war

source:AFP