KYIV (Reuters) - Ukraine has lost over 40% of the territory in Russia's Kursk region that it rapidly seized in a surprise incursion in August as Russian forces have mounted waves of counter-assaults, a senior Ukrainian military source said.
The source, who is on Ukraine's General Staff, said Russia had deployed some 59,000 troops to the Kursk region since Kyiv's forces swept in and advanced swiftly, catching Moscow unprepared 2-1/2 years into its full-scale invasion of Ukraine.
"At most, we controlled about 1,376 square kilometres (531 square miles), now of course this territory is smaller. The enemy is increasing its counterattacks," the source said.
"Now we control approximately 800 square kilometres (309 square miles). We will hold this territory for as long as is militarily appropriate."
The Kursk offensive was the first ground invasion of Russia by a foreign power since World War Two and caught Moscow unprepared.
With the thrust into Kursk, Kyiv aimed to stem Russian attacks in eastern and northeastern Ukraine, force Russia to pull back forces gradually advancing in the east and give Kyiv extra leverage in any future peace negotiations.
But Russian forces are still steadily advancing in Ukraine's eastern Donetsk region.
The Ukrainian General Staff source reiterated that about 11,000 North Korean troops had arrived in the Kursk region in support of Russia, but that the bulk of their forces was still finalising their training.
The Russian Defence Ministry did not immediately respond to a Reuters request for comment on Kyiv's freshest assessment of the state of play in the Kursk region. Reuters could not independently verify the figures or descriptions given.
Moscow has neither confirmed nor denied the presence of North Korean forces in Kursk.
Ukraine's armed forces chief said on Nov. 11 that its beleaguered forces were not just battling crack Russian reinforcements in Kursk but also scrambling to reinforce two besieged fronts in eastern Ukraine and bracing for an infantry assault in the south.
THREATENING RUSSIAN ADVANCE IN EASTERN UKRAINE
The General Staff source said the Kurakhove region was the most threatening for Kyiv now as Russian forces were advancing there at 200-300 meters (yards) a day and had managed to break through in some areas with armoured vehicles backed by anti-drone defences.
The town of Kurakhove is a stepping stone towards the critical logistical hub of Pokrovsk in the Donetsk region.
Overall Russia has about 575,000 troops fighting in Ukraine at the moment, the Ukrainian General Staff source said, and is aiming to increase its forces up to around 690,000.
Russia does not disclose numbers involved in its fighting, and Reuters could not independently verify those figures.
As Ukraine fights a bigger and better-equipped enemy, Kyiv has sought to disrupt Russian logistics and supply chains by hitting Russian weapons and ammunition depots, airfields, and other military targets well inside Russia.
Ukraine gained a freer hand to do so earlier this month after, according to sources familiar with the matter, President Joe Biden dropped his opposition to Kyiv firing U.S.-supplied missiles at targets deep inside Russia in response to North Korea's entry into the war.
Last week Ukraine fired U.S. ATACMS and British Storm Shadow
cruise missiles into Russia. One of the ATACMS targets was an arms depot about 110 km (70 miles) inside Russia.
Moscow vowed to respond to what it sees as an escalation by Ukraine's Western supporters. On Thursday, Russia launched a new medium-range ballistic missile into the Ukrainian city of Dnipro, in a likely warning to NATO.
Ukrainian officials are holding talks with the United States and Britain regarding new air defence systems capable of protecting Ukrainian cities and civilians from the new longer-range aerial threats.
The Ukrainian General Staff source said the military had also implemented measures to bolster air defences over the capital Kyiv and planned similar steps for the city of Sumy in the north and Kharkiv in the northeast, both near front lines.
Russia now occupies a fifth of Ukraine and President Vladimir Putin has said he wants Kyiv to drop ambitions to join the NATO military alliance and retreat from four Ukrainian regions that he partially holds, demands Kyiv has rejected as tantamount to capitulation.
(This story has been refiled to say over 40% of the territory Kyiv seized in August, not over 40% of entire Kursk region, in the headline)