The Institute for the Study of War said on Thursday that Ukrainian troops had advanced 10 kilometres (six miles) into Russia, possibly the most serious border incursion of the conflict.
Pro-Kiev forces stormed Russia’s southwestern Kursk region on Tuesday morning, deploying about 1,000 troops and more than two dozen armoured vehicles and tanks, according to the Russian military.
Kiev has not officially commented on the operation.
Russia’s top general on Wednesday vowed to crush the incursion and push Ukrainian fighters back across the border.
“Ukrainian forces have confirmed advances of up to 10 kilometres (six miles) in Russia’s Kursk Oblast amid ongoing mechanised offensive operations on Russian territory,” the US-based Institute for the Study of War (ISW) said in its latest update.
It added, “The current confirmed extent and location of Ukrainian advances in Kursk Oblast indicate that Ukrainian forces have infiltrated at least two Russian defensive lines and one stronghold.”
The advance is centered on the military base in Sudzha, a town of about 5,000 people, located eight kilometers from the Ukrainian border.
Very little information has been given in this regard by Moscow-based officials.
But Russian military bloggers with ties to the military also reported that Kiev had made significant progress and lamented the deteriorating situation.
“The situation is complicated and continues to get worse,” blogger Yuri Podolyaka said in a post on Telegram.
He said the city of Sudzha was “filled with Ukrainian soldiers”.
“Sudjha is completely lost,” he said.
“The enemy is strengthening its positions, which indicates that the fighting is likely to last a long time,” the Dwa Mayora Telegram channel said.
Several military bloggers reported that Ukrainian troops have advanced toward the town of Korenevo, more than 25 kilometers from the Ukrainian border.
Russian energy giant Gazprom said on Thursday it would continue shipping gas through the Sudzha metering station, the final transit point for Russian gas heading to Europe via Ukraine.
Russia’s Defence Ministry said its forces had destroyed a US-made Bradley fighting vehicle used by Ukraine in the incursion and also shot down a Ukrainian drone in the region.
The governor of the Kursk region declared a local state of emergency on Wednesday evening, giving authorities the power to impose restrictions on movement to bring the situation under control.
Several thousand people have been evacuated from both sides of the border.
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