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Ukraine’s top intelligence agency has confirmed that an underwater drone strike critically damaged a Russian submarine at a naval base in Novorossiysk.

Getting into it: According to Ukraine’s Security Service (SBU), the attack was carried out using Ukrainian-developed underwater drones known as the “Sub Sea Baby.” The SBU said the operation was jointly conducted with the Ukrainian Navy and involved navigating an unmanned underwater vehicle into the heavily protected naval port of Novorossiysk on Russia’s Black Sea coast. Ukraine said the target was a Russian Kilo-class diesel-electric submarine that was docked at the pier at the time of the strike.

According to the SBU, the explosion caused critical damage, effectively putting the submarine out of action. Satellite imagery analyzed by independent firms appears to show damage to a section of the pier near where the submarine was docked, though the full extent of damage to the vessel itself cannot be independently confirmed. Ukraine maintains the blast occurred close enough to compromise the submarine’s propulsion or operational systems, preventing it from being redeployed.

If the damage is confirmed, this would be a major blow to Russia, as Kilo-class submarines are among the country’s most capable non-nuclear attack submarines. These vessels are designed for stealth, earning the NATO nickname “Black Hole” due to their low acoustic signature.

Another view: Russia has acknowledged that an underwater drone attack took place but has denied Ukraine’s claims of damage. The Russian Black Sea Fleet said the sabotage attempt failed and that no submarines or crews were harmed, insisting all vessels at Novorossiysk remain operational. Russian state media later broadcast footage it claimed showed the submarine intact, though analysts noted the video did not clearly show critical areas such as the stern or propulsion system.