Ukrainian troops appeared on the point of losing their hard-won foothold inside Russia's Kursk region on Wednesday as Moscow claimed further advances there and military bloggers on both sides said Kyiv's forces were withdrawing.

Russian forces have begun an assault on the town of Sudzha, the main population center in the Kursk region that was captured by Ukraine last year, a top Russian commander said on Tuesday. The advance puts Moscow on the verge of ending the first invasion of Russian territory since World War II.