Ukraine has begun firing on North Korean troops inside Russia for the first time since they were deployed in the conflict, a Kyiv official said.
They added that Pyongyang's units were struck in the Kursk region of Russia following a deployment that was criticised by the US and Ukraine's other Western allies.
US, South Korean and Ukrainian intelligence assessments say up to 12,000 North Korean combat troops are being sent by Pyongyang to the war under a pact with Moscow.
Andrii Kovalenko, the head of the counter-disinformation branch of Ukraine's Security Council, wrote on Telegram: "The first North Korean troops have already been shelled, in the Kursk region."
He provided no further details.
Western governments had expected that the North Korean soldiers would be sent to Kursk border region in Russia, where a three-month-old incursion by the Ukrainian army is the first occupation of Russian territory since the Second World War and has embarrassed the Kremlin.
The North Korean troops, whose fighting quality and battle experience is unknown, are adding to Ukraine's worsening situation on the battlefield.
Ukrainian defences, especially in the eastern Donetsk region, are buckling under the strain of Russia's nearly 1,000-day-long war
Russian advances have recently accelerated, with battlefield gains of up to 9kms (5.5miles) in some parts of Donetsk, the British Ministry of Defence (MoD) said on Tuesday on X, formerly Twitter.
It said Russia has superior troop numbers, and despite heavy casualties the Kremlin's recruitment drive is providing enough new troops to keep up the pressure.
Russia has held the battlefield initiative in Ukraine for the past year. Ukrainian officials have long complained that Western military support takes too long to arrive in the country.
In early October, Russian forces drove Ukrainian troops out of Vuhledar, a town perched on top of a tactically significant hill in eastern Ukraine.
It was part of a key belt of Ukrainian defences in the east. Russia's next targets are likely to be the key logistics hub of Pokrovsk and the strategically important city of Chasiv Yar.
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In the meantime, Russia has kept up its long-range aerial attacks on civilian areas of Ukraine, authorities say.
A Tuesday morning attack on the southern city of Zaporizhzhia killed six people and injured 16 others, regional governor Ivan Fedorov said.
The head of Ukraine's presidential office, Andrii Yermak, said the Russian attacks "must be stopped with strong action".
"A stronger position by [Ukraine's Western] allies is needed," he wrote on Telegram.
(c) Sky News 2024: Ukraine begins shelling North Korean troops inside Russia, Kyiv official says