Russia said on Sunday it was pushing into Ukraine's eastern industrial Dnipropetrovsk region for the first time in its three-year offensive – a significant territorial escalation amid stalled peace talks.

Moscow, which has the initiative on the battlefield, has repeatedly refused calls by Ukraine, Europe and US President Donald Trump for a full and unconditional ceasefire.

At talks in Istanbul last week it demanded Kyiv pull troops back from the frontline, agree to end all Western arms support and give up on its ambitions to join the Nato military alliance.

Dnipropetrovsk is not among the five Ukrainian regions over which Russia has asserted a formal territorial claim.

It is an important mining and industrial hub for Ukraine and deeper Russian advances into the region could have a serious knock-on effect for Kyiv's struggling military and economy.

Dnipropetrovosk was estimated to have a population of around three million people before Russia launched its offensive. Around one million people lived in the regional capital, Dnipro.

Russia's defence ministry said forces from a tank unit had "reached the western border of the Donetsk People's Republic and are continuing to develop an offensive in the Dnipropetrovsk region".

The advance of Russian forces into yet another region of Ukraine is both a symbolic and strategic blow to Kyiv's forces afer months of setbacks on the battlefield.

There was no immediate response from Ukraine to Russia's statement.

Moscow in 2022 said it was annexing the frontline Donetsk, Kherson, Lugansk and Zaporizhzhia regions, which it did not have full control over.

In 2014, it seized the Crimean peninsula following a pro-EU revolution in Kyiv.

In a set of peace demands issued to Ukraine at the latest talks, it demanded formal recognition that these regions were part of Russia – something Kyiv has repeatedly ruled out. (AFP)