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.

Pro-Russian war blogger Two Majors said a major battle was under way for Sudzha and that Russian forces had surprised Ukrainian soldiers by entering the area via a gas pipeline.

Russian special forces walked inside a gas pipeline to strike Ukrainian units from the rear in the Kursk region, Ukraine’s military and Russian war bloggers reported, as Moscow claimed fresh gains in its push to recapture parts of the border province that Kyiv seized in a shock offensive.

Ukraine is rushing more troops to hold the line in Kursk, and there is heavy fighting underway in Russia's region of Kursk, where Moscow's forces have been regaining ground, pushing out the Ukrainians.