New images have come to light which appear to confirm previous reports of Russian “boots on the ground” in Syria, aiding Bashar al-Assad’s overstretched forces defend regime strongholds from advancing rebel armies.

The pictures appear to be taken in a variety of locations in western Syria, including Homs and the key port city of Tartus. They show Russian fighters posing with weapons in front of Russian and Syria flags, and portraits of the countries’ respective leaders Vladimir Putin and Bashar al-Assad.

The latest pictures follow a mounting video evidence and eye-witness testimony of Russia’s increased direct military intervention on behalf of its embattled Syrian allies, even as the United States continues to hesitate over its own stance towards the conflict.

A recent video released by the pro-regime National Defense Forces militia during clashes with rebels near Latakia includes the distinct sound of voices given orders in Russian to the gunner in a Russian-made BTR-82A fighting vehicle.

Listen: Russian orders on key Syrian battlefield

Russia has provided crucial military and financial support to the Assad regime since the start of the Syrian uprising in 2011, including advanced military hardware and military advisers. But the presence of Russian soldiers fighting on the front lines is a new and potentially game-changing development, which further complicates things for western powers hoping for Assad’s ouster.

It also reveals the degree to which Assad’s own forces – including the Syrian army and special forces, and an array of indigenous and foreign pro-regime militias – are struggling to cope with resurgent rebel forces in the both the north and south of the country.