A video posted on Ukrainian media outlets on Friday showed Ukrainian soldiers in control of a gas measuring facility in the town of Sudzha inside Kursk region, where Russia says it has been battling a Ukrainian military incursion for four days.
The soldiers in the 29-second video, shown in a building marked with the logo of Russian gas concern Gazprom, said they were also in control of the town of Sudzha.
"The town is controlled by the Armed Forces of Ukraine, the town is calm, all buildings are intact," a soldier in the video said.
"The strategic Gazprom facility is under the control of the 99th mechanised battalion of the 61st separate steppe brigade. Wishing everyone a peaceful sky."
Reuters could not immediately verify the video and the General Staff of the Ukrainian military had no comment.
Ukraine's military -- and President Volodymyr Zelenskiy -- have adopted a policy of strict silence concerning the armed incursion into Kursk region.
The video was the first demonstration of Ukrainian gains or control on the Russian side of the border.