According to Ukraine’s Security Service, its underwater Sub Sea Baby drones were deployed to attack Russia’s Novorossiysk naval base, striking and disabling its Project 636.3 Kilo-class submarine.
The Russian submarine was carrying Kalibr cruise missiles, but is now out of action according to Ukraine’s Security Service, SBU. This marks the first time the country has used underwater drones for such an attack.
The SBU said Sub Sea Baby underwater drones blew up a Russian submarine 636.3 “Varshavyanka,” which is known as the Kilo class according to its NATO reporting name. According to SBU, the submarine cost Russia up to €340 million. However, after Ukraine’s attack is has now sustained critical damage and “was effectively put out of action.”
As reported by the New York Times, Ukraine’s Security Service stressed the strategic importance of the target, as the Russian submarine “carried four launchers for Kalibr cruise missiles, which the enemy uses to strike targets in Ukraine.” Moscow has repeatedly used Kalibr missiles in long-range strikes against the country, including attacks on energy facilities and civilian infrastructure.
According to Ukrainian authorities, the operation was conducted jointly by the 13th Main Directorate of Ukraine’s Security Service military counterintelligence and the Naval Forces of the country.
“Given the international sanctions that have been imposed, the construction of a similar submarine could now cost over €420 million,” the SBU said.
Ukrainian military blew up a Russian submarine right in the harbour of Novorossiysk. They say that a Sub Sea Baby underwater drone was used. pic.twitter.com/rSvX45SHpZ
— Boris Alexander Beissner (@boris_beissner) December 15, 2025
According to officials, this marked the first time in history that such underwater drones were used successfully against a submarine of this class. They noted that this demonstrates the further evolution of Ukraine’s maritime campaign. Kilo-class vessels are not nuclear-powered and do not carry nuclear-armed ballistic missiles, according to the New York Times.
Following the drone strike on Monday, the SBU stated “the damaged boat was forced to remain in the port of Novorossiysk due to successful special operations by Sea Baby surface drones, which drove Russian ships and submarines out of Sevastopol Bay in the temporarily occupied Crimea.”
While Russia has confirmed the attack, it has denied that its submarine had been damaged.
In the past few years of the war against Ukraine by Russia, Kyiv has intensified its use of domestically produced maritime drones. These are used to push Moscow’s navy to ports along Russia’s coastline, including the one in Novorossiysk, a key naval hub which Ukraine has recently been targeting.
Officials say the operation was conducted by the Security Service in cooperation with the Navy, on a day when President Volodymyr Zelenskyy met with US negotiators and European leaders in Berlin to discuss peace proposals. Meanwhile, the successful strike appears to back Zelenskyy’s claim that Ukraine can continue to fight back and to pose a threat to Russia if no agreement is reached.
“Today, achieving results on the front line is crucial so that Ukraine can achieve results in diplomacy,” Zelensky said on Friday. This came when he was visiting Ukrainian positions close to the northern frontline town of Kupiansk, where it claims its forces recently encircled dozens of Russian soldiers.
“This is exactly how it works: strong positions inside the country translate into strong positions in negotiations to end the war,” Zelensky added.
