Ukraine claims successful UUV strike on Russian Kilo-class submarine

Images released by the SBU on 15 December 2025 showed the moment of the purported UUV explosion, with the Kilo II submarine seen just to the left of the detonation. (Security Service of Ukraine)

The Security Service of Ukraine (SBU) claimed to have damaged a Russian Navy Kilo II (Project 636.3 Varshavyanka) conventionally powered submarine (SSK) in port in Novorossiysk, in an online post on 15 December.

The SBU said in the post that in a joint operation with the Naval Forces of Ukraine, the 13th Main Directorate of Military Counterintelligence used a “Sub Sea Baby”, which it called an unmanned underwater vehicle (UUV) to approach and explode a charge near the stern of the Kilo II, while the submarine was alongside.

“As a result of the explosion, the submarine suffered critical damage and was actually put out of action,” said the SBU.

Before the explosion, three Kilo II-class boats were seen moored in the same section of the base. After the explosion, two of the boats had been moved, while the one closest to the detonation had not moved and appeared visibly down at the stern.

All of the Russian Navy's Kilo II-class submarines are equipped to launch both the SS-N-30a ‘Sagaris' (3M‐14 ‘Kalibr') subsonic, two-stage, conventionally armed, land-attack cruise missile and the SS-N-27a ‘Sizzler' (3M-54 ‘Kalibr') anti-ship missile from their torpedo tubes.