• Ukrainian special forces share photos on social media purporting to show their officers in town.
• Kupiansk is a vital supply hub for Russian forces in eastern Ukraine.
• Ukraine also making gains in the south of the country near the southern city of Kherson.

Ukrainian forces have entered the key eastern town of Kupiansk as their rapid counter-attack gains ground., Officials confirm.

Kupiansk, a vital supply hub for Russian forces in eastern Ukraine, fell a week after the invasion in February.

Ukrainian special forces shared photos on social media purporting to show their officers in town.

The advances would be the most significant since Russia’s withdrawal from the areas surrounding Kyiv in April.

If confirmed – and maintained – the gains would be used to demonstrate that Ukraine’s army is capable of retaking Russian-occupied territory, even as the country continues to seek Western military assistance.

They would be a humiliating setback for Russia, which had invaded the area early in the war.

Ukraine had advanced 50 kilometres (31 miles) into previously Russian-held territory, according to UK defence officials.

“Russian forces were likely taken by surprise,” the UK Ministry of Defence said. “The sector was only lightly held and Ukrainian units have captured or surrounded several towns.”

Ukraine launched its eastern counter-offensive earlier this week, while international attention was focused on an expected advance near the southern city of Kherson.

According to analysts, Russia redirected some of its most experienced troops to defend the city.

However, in addition to making gains in the east, Ukraine is also making gains in the south, according to an official.

According to Nataliya Gumenyuk, a spokesperson for Ukraine’s southern command, they have advanced “between two and several dozens of kilometres” along that front.

Observers in the east suggested that Ukraine was attempting to seize Kupiansk and gradually encircle thousands of Russian troops near the nearby city of Izyum.

On social media, Ukrainian officials appeared to show Ukrainian troops holding up the country’s flag in front of Kupiansk city hall, with the Russian flag at their feet.

“We are moving forward,” General Valeriy Zaluzhnyi, commander of Ukraine’s armed forces, wrote in a Facebook update on Friday afternoon. “We clearly know what we are fighting for and we will definitely win.”

Ukraine’s President Volodymyr Zelensky said during his nightly address from Kyiv that his forces are “gradually taking control of new settlements” and “returning the Ukrainian flag and protection for all our people.”