Russian authorities say they have foiled a plot involving hundreds of explosive-laden boot insoles allegedly smuggled into the country and disguised as humanitarian aid for soldiers fighting in Ukraine.

According to Russia's Federal Security Service (FSB), the agency seized 504 "heated" insoles—winter gear designed to keep feet warm in cold conditions—that were rigged with small explosive charges. The FSB claims each pair contained explosives equivalent to about 1.5 grams of TNT, enough to detonate when connected to a power source and potentially sever part of a soldier's limb.

The devices were reportedly destined for Russian troops in the "special military operation zone," the Kremlin's term for its war in Ukraine. Russian state media, including TASS, reported that the shipment was labeled as humanitarian aid to bypass scrutiny.

A foreign national born in 1994, identified by the FSB as a citizen of Tajikistan, was detained in Moscow. Authorities allege he was acting on instructions from a Ukrainian handler and was involved in smuggling the items from Poland through Belarus. The FSB directly blamed Ukrainian intelligence services for organizing the operation.

"Detonation occurs when the insoles are connected to a power source and is designed to sever a part of a serviceman's limb when they are used during combat missions," the FSB said in a statement.The agency also claimed the plot was part of a broader series of alleged sabotage attempts, including efforts to acquire drones in Moscow that could be turned into explosive devices for attacks in the Russian capital.