Newly released footage shows Russian forces striking a Ukrainian town, using what pro-Kremlin sources have claimed is one of the most potent non-nuclear weapons in the world.

On Tuesday morning, videos began circulating on Russian and Ukrainian media of a “vacuum bomb” being dropped on the town of Vovchansk in the country’s northeastern Kharkiv Oblast.

Ukrainian news agency InsiderUA posted the video to its Telegram channel, citing Russian military bloggers who said that the bomb was the ODAB-9000, a three-ton glide bomb sometimes referred to as “the father of all bombs.”

A thermobaric or “vacuum” bomb draws in oxygen to generate intense, high-temperature combustions. According to the International Review of the Red Cross, an international law-focused academic journal produced by the humanitarian organization, the use of thermobaric weapons in built-up, civilian areas could constitute a war crime.