Russia said on Monday its forces had made important gains in eastern Ukraine while continuing to fend off a new Ukrainian offensive inside the Kursk region of western Russia, where a second day of fierce fighting was under way.

Russian forces continue to make costly but consistent gains in the Donetsk region in eastern Ukraine. They are steadily grinding down a pocket of resistance around the town of Kurakhove and are also fighting to envelop the larger nearby city of Pokrovsk, Ukrainian soldiers and officials said.

Ukrainian President Volodymyr Zelenskiy said on Monday that Russia had suffered heavy losses in five months of fighting Ukrainian forces in southern Russia's Kursk region, with nearly 15,000 killed.

Ukraine launched a new offensive in Russia's Kursk region Sunday, Moscow and Kyiv said. Ukrainian forces had captured about 500 square miles of the western Russian province in a surprise incursion in August, but Russian and North Korean troops are believed to have retaken 40-50% of that area.

Ukraine appeared to launch a fresh offensive Sunday in Russia’s border region of Kursk, where Kyiv’s forces have held territory for several months.