MOSCOW: Russia on Thursday issued a stern warning to US forces and their allies in Syria, saying it has deployed Russian special forces alongside Syrian government troops in the battle to recapture the strategic city of Deir Al Zor and that Moscow would retaliate if the Russians come under fire.

The Russian Ministry of Defence said the US-backed Syrian Democratic Forces have already shelled Syrian government positions outside of Deir Al Zor twice in recent days.

The Russian special forces’ deployment raises the spectre of a direct confrontation on the ground between Russian forces and pro-Syrian troops they back on one side, and the US-supported Kurdish-led Syrian forces on the other. US special forces are also operating with the SDF, providing artillery and other support.

“Syrian forces have twice come under massive mortar and rocket artillery fire coming from the areas on the eastern bank of the Euphrates where SDF fighters and US special forces are deployed,” Russian Defence Ministry spokesman Major General Igor Konashenkov said.

Konashenkov said the warning was delivered to the US military command. Russian special forces have been deployed to help Syrian government forces fighting the Daesh terrorists outside Deir Al Zor, he also said on Thursday.

“Attempts to open fire from SDF-controlled areas would be immediately met with retaliation,” he said. “The firing positions in those areas will be immediately destroyed with all the arsenal at our disposal.”

However, a Syrian commander with the US-backed SDF denied Russian accusations of shelling, saying at least 7 kilometres of Daesh-held territory separates them from the Syrian government troops.

The SDF has already accused Russia of targeting its troops in Deir Al Zor in an air strike last week, a claim Moscow denied.

Russia began its operation to support President Bashar Al Assad’s offensive against Daesh in Syria in 2015 but has mostly focused on providing air cover to government troops on the ground.

The campaign for Deir Al Zor, Syria’s largest eastern city, is caught up in a race between government troops and the US-backed Syrian Democratic Forces.

In the past two weeks, the pro-government forces, backed by Russian air cover and Iranian-allied militiamen, gained control of most of the city and crossed the Euphrates River to the area of SDF operations. Despite US comments that consultations between the two sides intensified to avoid confrontation on the ground, the trading of accusations has continued.

Ahmad Abu Khawla, who commands the SDF unit in Deir Al Zor that is leading the fight in the oil-rich province, told AP that his troops have not fired at Syrian government forces. He also accused Russia of picking a fight and of seeking to obstruct the US-backed advance.

Any aggression against his forces will be reciprocated, Abu Khawla said.

“We are far from them, Daesh is between us,” Abu Khawla said in a voice message from Deir Al Zor. “We didn’t fire a single bullet toward the regime” forces.

On Wednesday, Abu Khawla said his troops had redirected their battles away from the river to fight Daesh terrorists deeper in the eastern desert. The Syrian forces crossed to the eastern side of the river earlier this week, bringing them just kilometres away from SDF forces.

The Russian-backed offensive on Deir Al Zor began on September 5, when the Syrian forces breached a nearly 3-year old siege on its troops north of the city. Syrian troops now control roughly 85 per cent of the city and expect to gain full control of it in the coming week, Konashenkov said.

A Syrian government offensive late on Wednesday captured two villages on the Euphrates’ western bank, liberating about 16 square kilometres of land, Konashenkov also said.

The development comes as the battle for the Daesh stronghold of Raqqa, north of Deir Al Zor, is reaching its “final stages”, the SDF said on Wednesday, nearly four months after the offensive began.

Less than 300 militants remain holed up in Raqqa, which has witnessed an intense bombing campaign, particularly in the last few days, according to the Britain-based Syrian Observatory for Human Rights that monitors the war.

The campaign to take Raqqa began in June in a quick advance after a breach of the wall of the Old City, a major fortification for the militants. But it has since slowed down as the forces faced mounting resistance from the militants.