Russia on Sunday announced a cross-border offensive had captured territory in Ukraine鈥檚 Sumy region for the first time since 2022 as Kyiv struggles to hold onto territory in Russia鈥檚 neighbouring Kursk region.
Russia also claimed a new village in the Kursk region as its troops pushed on against Ukrainian soldiers who had seized territory there.
Kyiv wants to use the territory it holds in Kursk as a potential bargaining chip in any peace negotiations.
US and Ukrainian negotiators are set to meet for talks in Saudi Arabia next week, with US president Donald Trump鈥檚 administration keen to agree on a ceasefire and a 鈥榝ramework鈥� for a peace agreement.
The US has cut off Ukraine鈥檚 access to intelligence sharing and satellite data in a bid to force it to negotiate.
The Russian defence ministry said in a briefing that its forces, in a counter-offensive, had 鈥榣iberated鈥� the small village of Novenke in Sumy near the border with Kursk.
Russia briefly occupied parts of Sumy at the start of its all-out invasion in 2022 but has not conquered any territory there since.
Russian president Vladimir Putin said in mid-February that his forces had entered this part of northeastern Ukraine, a claim branded a 鈥榣ie鈥� by Kyiv, although it has acknowledged isolated attacks.
Novenke is located about a kilometre from Kursk and Russian military bloggers said its capture brought troops closer to blocking a major Ukrainian supply route.
Kyiv has not yet commented on Russia鈥檚 claim to have captured Novenke.
Ukraine鈥檚 Centre for Countering Disinformation on Saturday denied reports of a 鈥榤assive breakthrough鈥� by Russia, saying its forces were destroying small groups trying to cross the border.
Russia on Sunday announced the recapture of the village of Lebedevka in Kursk, bringing its troops closer to taking back the Ukraine-held town of Sudzha, about 10 kilometres away.
Ukraine launched its incursion into Kursk last August, seizing territory as a buffer zone.
But since then, Russia has taken back more than two-thirds of the territory.
A Russian army commander, Apti Alaudinov, wrote on Telegram on Saturday that 鈥榓ll units have launched a large-scale offensive across all areas on the Kursk section of the front鈥�.
A Russian military blogger, Yevgeny Poddubny, on Sunday wrote that the Kursk incursion 鈥榠s in its final phase鈥�.
Prominent Ukrainian journalist Yuriy Butusov wrote on Sunday that holding onto the Kursk territory was no longer tactically justified.
Ukraine鈥檚 General Staff on Saturday confirmed reports that Russian special forces had used an underground gas pipe to reach the outskirts of the main town controlled by Ukraine in the region, Sudzha.
Kyiv said its aerial reconnaissance had spotted the troops, who were 鈥榖eing detected, blocked and destroyed鈥�.
Russian military bloggers wrote that troops crawled some 15 kilometres through a pipe with a diameter of 1.4 metres.
They hailed the attack as a feat, said the troops had achieved their objective, and that fighting was on-going in Sudzha.
Russia supplied gas to Europe via Ukraine until January of this year and Sudzha was a hub for transferring and measuring gas.
Russia also claimed the capture of another village in east Ukraine.
Its troops are advancing in the Donetsk region and are close to crossing a symbolic border into the central Dnipropetrovsk region, which so far has been free of fighting.
The defence ministry said troops had taken the village of Kostyantynopil, around 13 kilometres from the regional frontier and 50 kilometres west of the large Russian-held city of Donetsk.
Russia鈥檚 advances come as the prospect of peace talks appears increasingly likely, with Ukrainian and US negotiators meeting next week in Saudi Arabia.
US Middle East envoy Steve Witkoff said his team wanted 鈥榯o get down a framework for a peace agreement and an initial ceasefire as well鈥� at the talks set for Tuesday.
Ukrainian president Volodymyr Zelensky has said Ukraine is 鈥榝ully committed to constructive dialogue鈥�, while wanting its interests to be 鈥榯aken into account in the right way鈥�.
