Vladimir Putin rushed reinforcements to Kursk on Friday in an attempt to thwart a stunning Ukrainian advance that has seized swathes of Russian land.
State media aired footage of convoys of military hardware, including rocket launchers, artillery and tanks, heading to the border to bolster Moscow’s defences.
A Ukrainian Himars rocket strike destroyed one column of reinforcements, leaving 15 burned-out Russian vehicles and dead bodies strewn across the road.
Ukrainian troops posted a picture of themselves inside Russia in front of a road sign repainted in the Ukrainian language.
As the cross-border raid entered its fourth day, Moscow declared a state of emergency in the Kursk region as anger grew over the first invasion of Russian soil since the Second World War.
Mykhailo Podolyak, Ukraine’s presidential adviser, has said the raid could strengthen Kyiv’s hand in any future peace talks with Russia.
Elements of at least four Ukrainian brigades have taken part in the operation, which is estimated to have captured about 500 square kilometres of Russian territory.
The Institute for the Study of War, a US-based think-tank, said Ukrainian units had punched further into Russian territory in a “rapid advance”.
“Ukrainian forces are reportedly present in areas as far as 35 kilometres from the international border,” its analysts wrote in a daily battlefield update.
However, they warned Kyiv’s troops “most certainly” do not control that entire area.
Russia’s defence ministry said on Thursday that 1,000 Ukrainian troops supported by more than two dozen armoured vehicles had joined the fight.
On Friday, the ministry claimed that Ukraine had lost up to 945 soldiers and 102 pieces of equipment.
Military and political officials in Kyiv have remained tight-lipped over the operation and its goals.
Western analysts said the assault could prove a success if it forces Russia to reposition its troops from the front lines in eastern Ukraine, where they have been making significant gains.
Konrad Muzyka, a military analyst at Rochan Consulting, said: “It appears the Ukrainians want to capture as much Russian territory as possible, probably dig in, and force Russians to fight for it. There also could be an expectation that some forces would be redirected from other areas, such as Kharkiv and Donetsk Oblasts.
“In this context, Kyiv could be conducting a ‘reverse-Kharkiv’ [Russian attack in May] operation to force Russians to spread their forces and ease pressure elsewhere.”
Yesterday, Britain’s Ministry of Defence said Moscow’s soldiers were within 10 miles of Pokrovsk, a key Ukrainian garrison town in the Donetsk region.
Meanwhile, both Russia and Ukraine carried out long-range aerial attacks.
As Kyiv continued to fight on Russian soil, Moscow’s forces launched a daylight missile strike on a supermarket and post office in the eastern Ukrainian town of Kostyantynivka, killing 12 civilians and injuring 44 more, Volodymyr Zelensky, Ukraine’s president, said.
Officials shared footage of a plume of smoke rising above the remains of the building as rescue workers tried to free shoppers trapped under the debris.
Another image showed what officials claimed to the remains of a child in a body bag who had died in the strike.
“Russia will answer for this terror,” Mr Zelensky wrote on the Telegram messaging app.
“We will do everything to ensure that the world continues to be with Ukraine, supporting our defence and saving the lives of our people.”
The Ukrainian Himars strike on the Russian reinforcement convoy was described by military bloggers as one of the bloodiest of the entire war.
The Telegraph geolocated the two video clips to the E38 highway in the Russian town of Oktyabr’skoe, more than 20 miles from the border with Ukraine.
The convoy was likely travelling to reinforce the Russian presence in the settlement of Korenevo about 12 miles away, the closest point Russian sources have reported combat.
“Many dead, some of the vehicles burned to the ground. It looks like the entire column was carrying infantry,” a Russian Telegram channel wrote of the strike.
“They were armed, most likely a platoon per vehicle. 3-4 companies – an entire battalion was destroyed.
“Judging by the appearance of the column, about half were killed. This is one of the bloodiest and most massive strikes (most likely Himars) in the entire war.”
The Ukrainian Unian news agency reported that Moscow could have lost “200 to 490 people in what could become one of the largest one-time losses since the beginning of the full-scale war”.
Meanwhile, Ukraine’s SBU security service carried out an overnight drone attack on Russia’s Lipetsk air base, which is almost 200 miles from the border and east of the current fighting in Kursk.
Ukrainian officials said several warehouses packed with ammunition were detonated in the attack, destroying or damaging up to 700 glide bombs being stored.
Several dozen fighter jets and military helicopters were also at the base, Ukraine’s general staff said.
Local authorities in Lipetsk ordered a state of emergency, prompting mass evacuations from nearby towns.
Video of the incident showed the night sky being illuminated by multiple explosions as the ammunition “cooked off” after the initial drone strikes.
