In another photograph, four soldiers in battle fatigues posed in front of boxes of Russian ammunition piled high. Other images showed the devastation and destruction after a month’s fighting.

The Facebook page went on: “Today, the 93rd Mechanised Brigade Kholodnyi Yar, with the help of territorial defence forces and local partisans, has liberated the city of Trostyanets in the Sumy region from the Russian occupation forces.

“Kholodnyi Yar fighters have managed to expel the ‘elite’ Russian ground force troops, the Kantemyr tank division [4th Guards]

“This was preceded by the defeat of the command post and the leadership of the 96th Separate Reconnaissance Brigade in the first days of the defence of Okhtyrka and the battles for Trostyanets.

“After a series of setbacks, the Russian army has fled Trostyanets, leaving behind weapons, equipment and ammunition that the 93rd Brigade will use to liberate other Ukrainian cities from occupation.”

The Russian occupation of the town will now be subject to war crime investigations. The regional prosecutor’s office in Sumy opened a file after it was claimed that Russian troops had thrown hand grenades at civilians protesting against the Kremlin takeover of the town on March 18. The blast killed two men.

Philip Ingram, a former colonel in British military intelligence, said: “Trostyanets is a town on a significant north-south route between Sumy and Okhtyrka. If Ukraine has control of that road, then you are seriously restricting Russia’s ability to manoeuvre. 

“Any roads Ukraine takes back impacts Russia’s ability to move around. The Russians are constrained to the roads and control of the junctions gives you firing positions straight down them.”

It remains unclear where the Ukraine defensive positions are in the region. However, their ability to mount counter-attacks a month after the invasion suggests Russia has failed to land knockout blows – even in areas close to its border, where supply lines are shorter and logistics are in theory less problematic. 

Mr Ingram said that a combination of hand-held anti-tank weaponry supplied by the West, mainly Javelins and N-Laws, were damaging the Russian forces, along with drone strikes. Ukraine armoured infantry still appears to be able to manoeuvre along battle lines, with the Kremlin having failed to gain air superiority to knock out Ukrainian tanks.