Russia said on Tuesday that its troops had retaken over 100 square kilometres (38.6 square miles) of territory and 12 settlements in its Kursk region as part of an offensive to force the Ukrainian army to flee from western Russia.
The Russian advances threaten to encircle thousands of Ukrainian soldiers just as Ukraine holds talks with top U.S. diplomats in Saudi Arabia on Tuesday.
"Units of the North group of forces liberated 12 settlements during the offensive... and more than 100 square kilometres of the territory of the Kursk region," Russia's defence ministry said.
The ministry listed the settlements as Agronom, Bogdanovka, Bondarevka, Dmitryukov, Zazulevka, Ivashkovsky, Kolmakov, Kubatkin, Martynovka, Mikhaylovka, Pravda, and Yuzhny.
Ukrainian troops seized at least 1,300 square km (500 square miles) of the Kursk region in August in what Kyiv said was an attempt to gain a bargaining chip in future negotiations and to force Russia to shift forces from eastern Ukraine.
It was the most serious attack on Russian territory since the Nazi invasion of the Soviet Union in 1941, and seen as a way for Ukraine to embarrass the Kremlin by taking a chunk of Russian land.
Ukraine's top general said on Monday that Ukrainian troops fighting in Kursk were not at risk of encirclement, despite a recent counteroffensive by Russian forces that has included North Korean troops.
General Oleksandr Syrskyi said that the situation was under control, but indicated that Ukrainian forces have been pulling back.
"The units are taking timely measures to manoeuvre to advantageous positions for defence," he said.
Russian advances in Kursk and inside Ukraine, combined with Donald Trump's upending of U.S. policy on Ukraine and Russia have raised fears among European leaders that Ukraine will lose the war and that Trump is turning his back on Europe.
Russian special forces crept for miles through a gas pipeline near the town of Sudzha at the weekend in an attempt to surprise Ukrainian forces in Kursk.
Reuters could not independently confirm battlefield reports from either side due to reporting restrictions at the front.
