Zelensky says Russia must feel the war as Ukraine presses attack

Ukrainian President Volodymyr Zelensky said Thursday that Russia needed to "feel" the consequences of its war as a major Ukrainian incursion across the Russian border stretched into a third day.

Pro-Kyiv forces stormed into Russia's southwestern Kursk region on Tuesday morning, deploying around 1,000 troops and more than two dozen armoured vehicles and tanks, according to the Russian army.

It appears to be the most significant Ukrainian attack into Russia since the war began, with independent analysts suggesting Kyiv's troops had advanced up to 10 kilometres into Russia.

"Russia brought the war to our land and should feel what it has done," Zelensky said in his evening address, without directly referring to the offensive.

"Ukrainians know how to achieve their goals. And we did not choose to achieve our goals in the war," he added.

Russia's defence ministry said Thursday its troops were "continuing to destroy" armed Ukrainian units and were using air strikes, rocket and artillery fire to try to push them back.

It said it had rushed in reserves and was "thwarting attempts to break through" deeper into the Kursk region.

The independent US-based Institute for the Study of War said Ukraine had made significant territorial gains in the first two days of the incursion.

"Ukrainian forces have made confirmed advances up to 10 kilometres (six miles) into Russia's Kursk Oblast amid continued mechanised offensive operations on Russian territory," it said in its latest update.

"The current confirmed extent and location of Ukrainian advances in Kursk Oblast indicate that Ukrainian forces have penetrated at least two Russian defensive lines and a stronghold," it added.

Kyiv has not officially taken responsibility for the operation, but an aide to Zelensky said Moscow was to blame for the incursion.

"The root cause of any escalation, shelling, military actions, forced evacuations and destruction of normal life forms -- including within the Russian Federation's own territories like Kursk and Belgorod regions -- is solely Russia's unequivocal aggression," presidential aide Mykhailo Podolyak said Thursday on social media.

Russian President Vladimir Putin has called it a "large-scale provocation" by Kyiv and Russia's top general vowed on Wednesday to crush the incursion.

The US State Department expressed support for Kyiv without directly commenting on the operation.

The surprise attack appeared to catch Russia's army off guard, triggering criticism of its top brass by the country's influential military bloggers.

The Ukrainian advance has centred on the logistical hub of Sudzha, a town of around 5,000 inhabitants located eight kilometres from the Ukrainian border.

Russian military bloggers, who have links to the army, also reported Thursday that Kyiv had made significant advances.

"The situation is complicated and continues to worsen," blogger Yury Podolyaka said in a post on Telegram.

"Sudzha has been completely lost," he said.

Residents evacuated from Sudzha also reported a difficult situation, according to images shared by Russia's LDPR party.

"The situation is bad. There's no communication" with those who stayed behind, said Alexei, an ambulance worker waiting to receive humanitarian aid.

Another man also called Alexei, a volunteer, said the evacuees "feel abandoned".

The Dva Mayora Telegram channel said Ukraine was "entrenching, indicating that the fighting is likely to be long-term".

Many reported Ukrainian troops had advanced towards the town of Korenevo, more than 25 kilometres from the Ukrainian border.

AFP could not verify those reports.

Russian energy giant Gazprom said on Thursday it would continue shipping gas through the Sudzha metering station, the last transit point for Russian gas heading to Europe via Ukraine.

Moscow also said its forces had destroyed a US-made Bradley Fighting Vehicle that Ukraine was using in the incursion.

The Russian defence ministry had initially blamed a pro-Ukrainian "sabotage group" for the raid, but it has since said Ukraine's army is carrying it out.

Pro-Kyiv militia, including those made up of Russian citizens fighting against Moscow, have previously staged several cross-border raids.

But the latest incursion into the Kursk region appears to be the most successful and organised attempt by Ukraine to penetrate Russian territory.

Kyiv's objectives remain unclear, with some analysts suggesting it is an attempt to stretch Russia's army, forcing them to move units away from the eastern Donetsk region where they have been advancing.

The governor of Kursk declared a state of emergency in the region on Wednesday evening, a move that gives authorities the power to restrict movement in a bid to bring the situation under control.

Several thousand people have been evacuated on both sides of the border.