Around 10,000 Russian soldiers are fighting in Russia's Kursk region, about 90 sq km of which is controlled by Ukraine, Ukraine's top military commander said.
"We control about 90 square kilometers of territory in the Hlushkov district of the Kursk region of the Russian Federation, and these are our preemptive actions in response to a possible enemy attack," Oleksandr Syrskyi said without elaborating, in remarks released by his office for publication today.
The Ukrainian military said the activity in this area prevented Russia from sending a significant number of its forces to Ukraine's eastern region of Donetsk, where some of the heaviest fighting has taken place in the more than three-year-old full-scale invasion.
Mr Syrskyi's troops are repelling Russian forces along thefrontline, which stretches for about 1,200 km, where the situation remains difficult, the Ukrainian military said.
Russian gains have accelerated in May and June, though the Ukrainian military says it comes at a cost of high Russian casualties in small assault-group attacks.
While the military says its troops repelled Russian approaches toward Ukraine's Dnipropetrovsk region borders last week, the pressure continues in the country's eastern andnorthern regions.
The Russian military also continues its deadly drone and missile attacks on the Ukrainian cities further from the front, prompting Ukraine to innovate its approaches to air defence.
Ukraine's military said it currently destroys around 82% of Shahed-type drones launched by Russia but requires more surface-to-air missile systems to defend critical infrastructure and cities.
The military said the air force was also working on developing the use of light aircraft and drone interceptors in repelling Russian assaults which can involve hundreds of drones.
Ukraine also relies on its long-range capabilities to deal damage to economic and military targets on Russian territory, increasing the cost of war to Moscow.
Between January and May, Ukraine dealt over $1.3 billion in direct losses in the Russian oil refining and fuel production industry, energy and transport supplies as well as strategic communications, the Ukrainian military said.
It also dealt at least $9.5 billion more of indirect damagesthrough the destabilization of the oil refining industry,disruption of logistics and forced shutdown of enterprises, it added.
It was not clear whether the Ukrainian military included the damages from its operation "Spider's Web" which damaged Russian warplanes - and Ukraine said cost billions in losses - in the estimates.
Ukraine army chief vows to expand strikes on Russia
Ukraine's top military commander has vowed to increase the "scale and depth" of strikes on Russia in remarks made public Sunday, saying Kyiv would not sit idly by while Moscow prolonged its three-year invasion.
Diplomatic efforts to end the war have stalled in recent weeks.
The last direct meeting between the two sides was almost three weeks ago and no follow-up talks have been scheduled.
Russian attacks on Ukraine have killed dozens of people during the interim, including in the Ukrainian capital Kyiv, according to officials.
"We will not just sit in defence. Because this brings nothing and eventually leads to the fact that we still retreat, lose people and territories," Ukrainian commander-in-chief Oleksandr Syrsky told reporters including AFP.
Mr Syrsky said Ukraine would continue its strikes on Russian military targets, which he said had proved "effective".
"Of course, we will continue. We will increase the scale and depth," he said.
Ukraine has launched retaliatory strikes on Russia throughout the war, targeting energy and military infrastructure sometimes hundreds of kilometres from the front line.
Kyiv says the strikes are a fair response to deadly Russian attacks on Ukrainian infrastructure and civilians.
In wide-ranging remarks, Mr Syrsky also conceded that Russia had some advantages in drone warfare, particularly in making fibre-optic drones that are tethered and difficult to jam.
"Here, unfortunately, they have an advantage in both the number and range of their use," he said.
He also claimed that Ukraine still held 90 sq km of territory in Russia's Kursk region, where Kyiv launched an audacious cross-border incursion last August.
"These are our pre-emptive actions in response to a possible enemy offensive," he said.
Russia said in April that it had gained full control of the Kursk region and denies that Kyiv has a presence there.
Moscow occupies around a fifth of Ukraine and claims to have annexed four Ukrainian regions as its own since launching its invasion in 2022 - in addition to Crimea, which it captured in 2014.
Kyiv has accused Moscow of deliberately sabotaging a peace deal to prolong its full-scale offensive on the country and to seize more territory.
The Russian army said today that it had captured the village of Petrivske in Ukraine's northeast Kharkiv region.
Russian forces also fired at least 47 drones and three missiles at Ukraine between late Saturday and early Sunday, the Ukrainian air force said.
At least two people were killed in the attacks on Ukraine's eastern Donetsk region, including a 17-year-old boy, the region's governor said.
