Security Service releases night-vision video and claims a first-of-its-kind hit in Novorossiysk; Russia has not confirmed the damage.
KYIV, UKRAINE — Ukraine’s security service said Monday its new “Sub Sea Baby” underwater drones struck a Russian Kilo-class submarine inside the Black Sea port of Novorossiysk, releasing footage of a blast in the harbor and calling the operation a first in modern naval warfare.
Ukraine framed the strike as a milestone in its campaign to push Russia’s fleet away from launch sites used for cruise-missile attacks on cities. The claim arrives as both sides fight through winter and trade long-range blows against ports, fuel depots and shipyards. Kyiv’s Security Service, known as the SBU, said the submarine was critically damaged, but offered no serial number or name. Russian authorities did not immediately confirm any loss. Independent verification of the submarine’s status remained unclear late Monday, raising questions about the extent of the damage and whether the vessel sank or could be repaired.
The video released by Ukrainian officials shows a low-slung drone view moving at night toward moored ships before a white flash erupts against a dark shoreline, followed by a shock wave rippling across the water. The SBU said the strike occurred at Novorossiysk, a key Russian Navy base east of Crimea that has become a fallback port since repeated Ukrainian attacks on occupied Sevastopol. Ukrainian officials described the drone as a sub-surface variant of the “Sea Baby” platform already used in surface strikes, equipped for covert approach and a large explosive charge. “The target was a Project 636.3 submarine,” the security service said, referring to Russia’s diesel-electric Varshavyanka design, known in NATO reporting as an improved Kilo. The agency said the boat had been used to fire Kalibr cruise missiles at Ukraine.
Ukraine did not provide a date stamp for the footage, the number of drones used, or the warhead size. Local Russian authorities and the Defense Ministry offered no detailed account of the incident by Monday evening. Military bloggers on Russian social media channels posted unverified clips of emergency lights and smoke near the port. Satellite-tracking analysts said heavy cloud cover over the eastern Black Sea limited same-day imagery, leaving open whether the submarine was sunk at its berth, towed to shallow water, or only damaged. The Novorossiysk port authority listed no official disruptions, and civilian shipping trackers showed routine traffic entering and leaving the outer roadstead through the day. What happened inside the naval basin remained uncertain.
The port’s rising importance helps explain why it is now a frequent target. After losing ships to Ukrainian sea drones and missiles in 2023 and 2024, the Black Sea Fleet shifted more vessels from Sevastopol in occupied Crimea to Novorossiysk on Russia’s mainland coast. The improved Kilo submarines based there have launched Kalibr missiles against Ukrainian energy infrastructure and cities, forcing repeated nationwide air-raid alerts. Ukraine’s homegrown drone program expanded in response. Officials have previously publicized the “Sea Baby” family as modular craft built with domestic components and commercial electronics to skirt sanctions and lower costs. Kyiv credits earlier surface-drone attacks with damaging a landing ship in Feodosia, hitting an oil terminal in Novorossiysk, and forcing Russian warships to operate farther from Ukraine’s coast.
Even if the latest hit proves a disabling blow rather than a confirmed sinking, a Kilo-class boat is a complex asset to replace. The Varshavyanka series is built at the Admiralty Shipyards in St. Petersburg and fitted with Western-restricted microelectronics for guidance and sonar suites, according to open records. The subs are prized for very quiet running on battery and the ability to fire Kalibr missiles while submerged. Russia has lost or seen heavy damage to several large naval assets since the full-scale invasion, including the cruiser Moskva in 2022 and the submarine Rostov-on-Don during a 2023 missile strike in Sevastopol’s dry dock. Ukraine argues that each additional loss reduces the tempo of missile salvos and complicates Russian logistics along the Black Sea coast.
Ukraine’s claim also underscores how inexpensive, unmanned systems are reshaping the sea war. Surface drones the size of small boats have forced heavier ships behind layered booms and nets, with helicopter patrols and barges mounting machine guns along harbor approaches. An underwater variant adds a second axis of risk, slipping beneath surface barriers and striking at the waterline. Naval engineers say even a near miss can buckle a submarine’s outer hull and flood compartments through pierced cables and piping. But such attacks are hard to document in real time, particularly inside closed military ports. Without wreckage visible at the surface or clear imagery from inside the basin, assessments often rely on later commercial satellite passes or admissions tucked into procurement notices and repair contracts.
For now, the legal and procedural picture is straightforward: Ukraine claims an attack on a military target belonging to an invading force; Russia exercises control over Novorossiysk’s naval facilities and can restrict access and information. No casualties were confirmed by either side Monday. There were no immediate advisories of fuel spills or navigation hazards for civilian ships. Ukrainian officials said they would release additional materials “when operationally safe.” Russia typically issues brief communiqués about intercepts or “repelled” attacks; a more detailed statement could come in the next defense briefing or in local governor updates. Analysts will watch for dry-dock activity, tug movements inside the base, and any notice to mariners that could hint at salvage or clearance work.
In Kyiv and Odesa, the mood was restrained but resolute. “Every Kalibr that doesn’t launch is one fewer air-raid siren at night,” said Serhii Bratchuk, a spokesman for the Odesa regional military administration. Residents along Ukraine’s southern coast said they heard fewer cruise-missile alerts overnight but were cautious about drawing conclusions from one clip. In Novorossiysk, a port worker reached by phone said emergency crews were active near the naval sector before dawn and that access roads briefly tightened, adding, “We kept cargo moving.” A retired Ukrainian Navy officer called the underwater strike “a proof-of-concept with strategic effect,” arguing it will force Russia to harden defenses below the surface as well as above it.
As of late Monday, Ukraine stood by its account and promised more details once forces complete damage assessments. Russia had not presented its version of events. The next clues could come from new satellite imagery or official briefings later this week.
Author note: Last updated December 15, 2025.