Meanwhile, Ukraine’s President Volodymyr Zelensky called on his people not to panic amid Russia’s ongoing advance in the Kharkiv region that’s jeopardising a local city.

Ukrainians should trust in their army defending the country’s northeastern border area and not “yield to emotions” despite the fierce fight there and the “extremely difficult” situation on the outskirts of Vovchansk, Zelensky said in his regular evening statement on Sunday.

Along with several other towns and villages, Vovchansk – a city located only several kilometres from the border with Russia – is under constant fire from advancing Russian troops, according to local authorities who initiated a mass evacuation.

Ukraine’s troops are attempting a counter-attack near Vovchansk, Zelensky said.

“The advance in the Kharkiv region aims to stretch our forces and undermine their morale and motivation,” he said. “Defence battles have never been simple, and they become even more challenging when an enemy manages to instil fear.”

Zelensky’s comments were accompanied by statements from Vovchansk’s authorities, who assert that the Kremlin was spreading fake news by promoting a narrative that the local government had fled the city after its capture.

Russia’s defence ministry on Sunday claimed its troops had made deeper advances in the Kharkiv border region, “liberating” a total of nine settlements over the weekend.

The monitoring platform Deep State said Russia now occupies six villages in the area, north of Kharkiv, Ukraine’s second-largest city. Military authorities in Kyiv haven’t confirmed the capture of those locations, saying instead that fighting is ongoing.

“There are villages that have transformed from ‘a grey zone’ into a zone of fighting and invaders are attempting to dig in, in several of them, while others serve for their further advance,” Zelensky said.

Earlier the same day, Chief-in-Command of Ukraine’s army Oleksandr Syrskyi said that Russian forces were able to achieve “partial” success in several areas. He didn’t elaborate on the exact locations.

While Kyiv’s forces have repelled attempts by Moscow’s troops to break their defences in the nation’s northeast, the situation has “significantly worsened” in the past week and the situation in the Kharkiv region is “difficult,” he said.

The surprise Russian assault is likely to stretch Ukraine’s already outgunned and outmanned forces, as it may push Kyiv to redeploy some of its troops from the long front line in the east. Ukraine is trying to hold its ground as it awaits the arrival of US military aid.

The objective of Russia’s stepped-up offensive in the Kharkiv region appears to be to establish a “buffer zone” into Ukraine to minimise strikes into Russian territory.

The US-based Institute for the Study of War said Moscow’s troops continued to make tactically significant gains over the weekend “in likely less defended areas”.

The reported sizes of the amassed troops “indicate that Russian forces are not pursuing a large-scale operation to envelop, encircle, or seize Kharkiv City at this time,” ISW said.