Ukrainian underwater drones strike Russian naval base

Ukrainian strike underwater drones have attacked a Russian naval base in Novorossiysk, in what Ukrainian officials describe as the first combat use of underwater drones to disable a modern diesel-electric submarine.

According to Ukrainian sources, underwater drones known as “Sub Sea Baby” detonated beneath a Russian Project 636.3 submarine of the Varshavyanka class, known in NATO reporting as the Kilo class. The explosion caused critical damage to the submarine, effectively putting it out of action.

The submarine was carrying four launchers for Kalibr cruise missiles, Ukrainian officials said, underscoring the strategic importance of the target. Kalibr missiles have been used repeatedly by Russia in long-range strikes against Ukraine, including attacks on infrastructure and military facilities.

Ukrainian authorities said the operation was conducted jointly by the 13th Main Directorate of the Security Service of Ukraine’s military counterintelligence and the Naval Forces of Ukraine. The attack took place at the port of Novorossiysk, a key Russian naval hub on the Black Sea that has taken on greater importance since Ukrainian strikes forced Russian vessels to disperse from Crimea.

As reported by Ukrainian sources, the damaged submarine had been stationed in Novorossiysk after a series of special operations involving Ukrainian surface maritime drones, including the Sea Baby system. Those earlier attacks pushed Russian warships and submarines out of Sevastopol Bay in Russian-occupied Crimea, forcing Moscow to rely more heavily on ports along Russia’s mainland coast.

Ukrainian officials said this marked the first time in history that underwater strike drones have been used successfully against a submarine of this class. Project 636.3 submarines are among Russia’s most modern diesel-electric boats and are designed for low acoustic signatures, making them difficult to detect and track. The class is widely used by the Russian Navy and has also been exported to several foreign customers.

The Varshavyanka-class submarine targeted in Novorossiysk was reportedly unable to leave port following the explosion. Ukrainian sources said the damage was severe enough to remove the vessel from operational service, though no independent assessment has yet been released by Russian authorities.

Russia has not publicly confirmed the incident or commented on the condition of the submarine. In past cases, Moscow has either delayed acknowledgment of losses in the Black Sea or denied Ukrainian claims outright, even when satellite imagery or follow-on evidence later supported Kyiv’s account.

The use of underwater drones represents a further evolution of Ukraine’s maritime strike campaign. Over the past two years, Ukraine has relied heavily on unmanned surface and subsurface systems to offset Russia’s numerical advantage at sea. These systems have targeted warships, patrol vessels, landing ships, and port infrastructure, often deep behind Russian-controlled waters.