Ukraine has lost over 40% of the territory in Russia's Kursk region that it seized in a surprise incursion in August as Russian forces have mounted waves of counter-assaults, a senior Ukrainian military source said.

The Ukrainian source revealed that their forces initially controlled up to 1,376 square kilometres (531 square miles) of territory in Kursk but now hold around 800 square kilometres (309 square miles).

Faced with waves of counterattacks from nearly 60,000 Russian troops, Ukraine has lost more than 40% of the territory it once controlled in its August invasion of Kursk, Reuters reported, citing a member of the Ukrainian General Staff.

Ukrainian President Volodymyr Zelensky said Russia has deployed nearly 50,000 troops to Kursk, the southern Russian region where Kyiv launched its surprise counteroffensive in the summer.

Experts tell Andy Gregory and Tom Watling that the real question is how much Kyiv’s troops are able to inflict casualties on the Russians as the price for taking the territory back

Russia has amassed a large force of tens of thousands — including recently arrived North Korean troops — to carry out an assault on the Ukrainian positions in Russia’s Kursk region expected in the coming days,