Footage shared on Telegram appears to show Russian soldiers crouching and moving through the pipeline in darkness toward the town of Sudzha, according to. In the video, the soldiers can be heard cursing and complaining about their commanders for sending them on the mission.

According to a pro-Kremlin blogger, Russian operatives walked about 9 miles inside the pipeline that Moscow had until recently used to send gas to Europe.

The front line inside Ukraine has become more static, Ukrainian soldiers say, even as Russia regains ground in its own Kursk region.