Russia is now moving reinforcements to the Kursk region, state-run media report, citing the country's defence ministry.

Multiple Grad rocket launch systems, artillery guns and heavy tracked armoury are being deployed in the region around the embattled town of Sudzha, Ria-Novosti and Tass news agencies report.

Ria-Novosti also published footage purporting to show a column of Russian military trucks moving into the Kursk region.

In the last few moments, we've received new figures from Ukraine's interior ministry following a Russian strike on a supermarket in Kostyantynivka, in Ukraine's eastern Donetsk region.

Ten people have been killed and another 35 injured, officials say.

Residential buildings, shops, and more than a dozen cars were also damaged, they add.

Emergency services continue to work at the scene, including police and paramedics.

Image source, Donetsk regional military administration

Now for some breaking news.

Ukraine says at least four people have been killed in a Russian artillery strike on a supermarket and a post office in the eastern Donetsk region.

At least 24 people were injured in the city of Kostyantynivka, Ukrainian President Volodymyr Zelensky says.

A number of people are still under the rubble, as a search and rescue operation continues.

"Russia will answer for this terror," Zelensky warns.

James Waterhouse
Ukraine correspondent, reporting from Kyiv

Image source, Getty Images / Russian Ministry of Defense

When Kyiv launched a cross-border raid into Russia’s Kursk region bordering Ukraine, the question from some military experts was: “Why?”

One of Ukraine’s biggest battlefield issues is manpower. Russia has more soldiers and is inching closer to the eastern Ukrainian town of Pokrovsk.

So, sending hundreds of Ukrainian soldiers into Russia itself is, shall we say, counterintuitive in the eyes of some.

But not all.

“It wasn’t accidental,” said war expert Kostyantyn Mashovets in a Facebook post. “It’s clearly part of one clear plan."

Mykhaylo Zhyrokhov, a military analyst, agrees. He told the BBC that Russia had been forced to redeploy some troops there from the front line in eastern Ukraine.

“If you look at official reports, there were significantly fewer Russian glide bombs dropped in the Donetsk area,” he said.

“That means the aircraft which carry them are now elsewhere in Russia.”

This incursion is extremely unlikely to be Ukraine looking to occupy Russian territory, but if pulling in Russian forces was a goal, it is quickly being realised.

• You can read more from James here

Elsewhere today, Ukraine's military says it's hit a military airfield deep inside Russia, destroying guided bombs stored in warehouses.

In a statement, the Ukrainian military reports a huge blaze and multiple detonations at the Lipetsk airfield, more than 350km (217 miles) from Ukraine's border.

The statement says the airfield is known for housing Russia's Su-34, Su-35 and MiG-31 war planes - but provides no further information about the overnight attack.

Lipetsk's regional authorities says a state of emergency is now in place in the area, confirming the detonations at an "energy infrastructure facility". Residents of four nearby villages are being evacuated.

Jaroslav Lukiv
Live reporter

Image source, Reuters

Russia's military says it's "continuing to repel" a Ukrainian cross-border incursion into the western Kursk region - a surprise attack now in its fourth day.

Reports suggest that Ukrainian troops are operating more than 10km (six miles) inside Russia - the deepest cross-border advance by Kyiv since Moscow launched a full-scale invasion in February 2022.

Ukraine has not openly admitted the incursion, but President Volodymyr Zelensky said late on Thursday that Moscow must "feel" the consequences for its invasion.

The Russian defence ministry says Ukraine lost more than 280 military personnel in the past 24 hours - a claim that has not been independently verified.