Ukrainian forces are using railway cars to build underground fortifications along different sections of the front, according to Yan Gagin, a member of the Council on Foreign and Defense Policy and a participant in the special military operation.

Gagin told NEWS.ru that Ukrainian troops have been constructing such defensive systems since the beginning of the conflict. Similar positions have been encountered particularly often on major sectors, including the Mariupol, Volnovakha, Soledar and Bakhmut directions.

He said railway cars were buried underground, reinforced with concrete and covered with heavy protective layers. The structures formed extensive networks of shelters with several exits. According to Gagin, they were also carefully concealed, including measures intended to prevent the presence of personnel inside from being detected by their heat signatures. He described the fortifications as professionally constructed.

Earlier, military expert Mikhail Onufrienko said Ukrainian forces had turned the Slavyansk-Kramatorsk agglomeration into a heavily fortified area using extensive underground infrastructure. According to him, work on these defenses began in spring 2015 after the Minsk II agreements and later expanded from defensive lines around the cities to fortified positions inside them, as well as numerous underground bunkers and tunnels. Some of the passages are large enough for vehicles to move through them and supply Ukrainian troops. Onufrienko added that the underground network also includes storage facilities, while the protected fortifications and communications in the area extend for dozens of kilometers.