Russia is deploying its most advanced battlefield tanks in Syria, in the latest sign that the Kremlin is being forced to escalate its intervention from an air to a ground war.

A report by the Iranian Fars news agency, supported by photographs circulating on social media this week, suggest that newly delivered T-90 tanks have been sent to support the Syrian regime’s advance south of Aleppo.

Two months after Moscow intervened militarily to shore up a Syrian regime that was crumbling under the pressures of war, the deployment of T90s seems intended to combat a flood of anti-tank missiles with which rebel forces have been able to destroy less capable tanks.

Experts say the Russian intervention is prolonging a conflict that has already claimed the lives of more than a quarter of a million Syrians, causing millions to flee abroad as world world powers pile in to join an escalating civil war.

The T-90 tanks are swaddled in explosive armour, causing most weapons used against them to detonate on impact. Pro-regime media have said that they will be manned by hastily trained Syrian operators, though experts have questioned that claim due to the high value nature of the tanks.

Although the vehicles have been used during conflicts in Chechnya and Ukraine, this is their first confirmed deployment to a war zone, according to Tim Ripley, an analyst who writes for Jane’s Defence Weekly.

Russia has denied that it is extending its Syrian war effort beyond air strikes and maintains that its troops are not engaged in ground combat. But recent developments suggest it is now getting sucked into a costly and possibly lengthy fight, due to the Syrian regime’s inability to capitalise on the initial intervention.

The deployment of the T90s appears to reflect Moscow’s frustration at this failure, as well as concern over the damage inflicted by the rebels’ anti-tank missiles, themselves supplied by the regime’s arch-rivals in the Gulf states and Turkey.

Despite a close and sustained air support, regime troops and their allied Shia militia have failed to recapture a single strategically important town or city from the assortment of rebel factions they have been battling.

Mr Ripley said the movement of T90s to south Aleppo appeared aimed at punching westwards through Aleppo province into Idlib, a region that has been under control of rebel groups including since their lightning sweep through the area at the beginning of this year.

Russia is also expanding an air base in Homs province in western Syria to accommodate its fighter jets, and was already using another, further east, for helicopter sorties, according to the Syrian Observatory for Human Rights, a Britian-based monitoring group.

The first, the Shayrat air base, is southeast of Homs city, and the second, at al-Tayas towards the Islamic State-controlled city of Palmyra, were likely to be used to strike the group in the area.

Russian military experts suggested that if the expansion of new bases is confirmed it could signal new offensive operations.

“Russia has expanded its operations against Isil since the bombing of a Russian civilian jet in Egypt in October,” said Vassily Kashin, a senior research fellow at the Moscow-based Centre for Analysis of Strategies and Technologies, a private think tank.

“But much of that has been done by long-range strategic bombers flying from Russia. When you need close coordination with ground troops and rapid reaction times, you need bases close to the front, especially if you’re using helicopters,” he added.

A strengthened Russian presence through Homs and central Syria would help the regime to re-take the strategically important town of Palmyra from Islamic State militants, seven months after the jihadist group took control of the area and began destroying its precious Roman ruins.

It could also secure an important natural gas field which links up to power stations that keep the lights on in the regime’s base, Damascus.