Ukraine’s armed forces have advanced some 30 kilometers into Russia’s western Kursk region since launching the assault last week, in what is by far the biggest Ukrainian incursion into Russia since the start of the full-scale war between the two countries in 2022.

According to Alexei Smirnov, the governor of the Kursk region, so far 121,000 residents have been evacuated, and a further 59,000 still need to leave. He added that Ukraine has seized 28 villages.

Reacting to the news of the Ukrainian offensive, Putin said on Monday that the “Defense Ministry’s main task is to push, to kick, the enemy out of Russian territory”.

"Losses have been mounting dramatically for the armed forces of Ukraine, particularly among the most capable units which the enemy has been sending to our border,” he continued, during a meeting with officials.

"The enemy will undoubtedly receive a worthy response, and there is no doubt that we will reach all our objectives."

Meanwhile, there were reports of Ukrainian troops digging trenches in western Russia, in a move suggesting that they intend to defend their positions and that no withdrawal is planned.

“The worst thing that can happen is a transition to trench warfare in the Kursk region,” Aleksandr Karachenko, a Russian military reporter, wrote on Monday. “The enemy is gaining a foothold in our ancestral territory.”

He added that once “the enemy picks up shovels” it will be difficult for Russian forces to evict them.

While Ukraine’s attack has embarrassed Moscow and provided Ukraine with a welcome boost to morale following months of defensive operations, Kyiv has remained coy about its military objectives in western Russia.

In an analysis of the operation published on Monday, Matthew Savill, military sciences director at the Royal United Services Institute, a British think-tank, warned of the dangers for Ukraine of trying to hold land.

“The main risk is that the Ukrainians choose to try and consolidate and hold ground that lengthens the front line, where the Russians already have a personnel advantage, without the ability to reinforce and defend against Russian counter-attacks (or that to do so thins the line elsewhere),” he wrote.

“For example, if airbases inside Russia aren’t hit, Russian air power will be able to use glide bombs against Ukrainian forces, even if dug in around Russian settlements.”