Near Kupyansk, Ukrainian servicemen attempted to organize a covert passage into the rear of Russian positions through an underground tunnel, but the attempt ended with personnel killed after a sudden soil collapse.

According to the Telegram channel SHOT, the Ukrainian command intended to repeat the Russian operation Potok, carried out in Kursk Region, when Russian Armed Forces fighters managed to get behind enemy lines through a pipe. To do this, a group of Ukrainian Armed Forces servicemen was brought for several nights in a row to a specially selected point where they were supposed to dig a large tunnel.

However, the work failed at the initial stage. According to the channel, the Ukrainian troops managed to dig only about five meters before a collapse occurred at a depth of 5–6 meters. Ukrainian Armed Forces fighters were buried under a layer of soil.