Ukraine has lost more than 40 per cent of the territory in Russia’s Kursk region that it seized in August, a senior Ukrainian military source said.

Russia had deployed 59,000 troops to the region since the surprise invasion by Kyiv’s forces, said the source, who is on Ukraine’s general staff.

“At most, we controlled about 1,376 square kilometres (531 square miles), now of course this territory is smaller. The enemy is increasing its counter-attacks,” the source said, reported by Reuters.

“Now we control approximately 800 square kilometres (309 square miles). We will hold this territory for as long as is militarily appropriate.”