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Novorossiysk (B-261)

At the end of September 2025, a Telegram channel known for its network of Russian intelligence sources reported that a Black Sea fleet submarine had run into “serious technical problems” while on a mission off Gibraltar, in the Mediterranean. The Novorossiysk submarine was at risk of exploding, it said, and according to online sleuths, later surfaced, giving away its location.

The news that a short-range Russian stealth hunter was circling in the Strait of Gibraltar first came to public attention on September 27. The anti-Kremlin Telegram channel VChK-OGPU reported that the 74-metre-long Kilo-class Novorossiysk “currently on combat duty in the Mediterranean” had experienced a technical failure, and that fuel was leaking into the bilge, the very bottom of the vessel hull.

“The submarine has neither the spare parts nor the qualified specialists onboard to fix the malfunction,” VChK-OGPU wrote, and warned that the sub “now poses an explosion hazard”. An alleged September 26 sighting of a submarine surfacing in the Strait of Gibraltar appeared to confirm its location. According to online sleuths, a US Navy maritime patrol plane also flew over the area where the submarine was spotted for several days in a row.

Neither Russian authorities nor state-controlled media confirmed the sub’s presence in the Mediterranean.

The Novorossiysk (B-261) is a diesel-electric attack submarine of the Russian Navy, serving as the lead ship of the Project 636.3 variant (NATO designation: Improved Kilo II) of the Kilo-class submarines. This class, originally developed by the Soviet Union's Rubin Design Bureau in the 1970s, is renowned for its stealth capabilities—earning the nickname "Black Hole" from NATO due to its low acoustic signature, making it one of the quietest non-nuclear submarines in the world. The Improved Kilo II enhances the original Kilo design with upgraded sensors, propulsion, and missile systems, including the ability to launch Kalibr cruise missiles (some variants nuclear-capable).

The Novorossiysk belongs to one of the more recent Kilo-class models, and was put into service in August 2014. It joined Russia’s Black Sea fleet in September 2024. Like other submarines in its category, the Novorossiysk’s main purpose is to operate in coastal waters where the seas are not too deep. It is equipped with torpedoes, however, which would make a potential fire onboard particularly dangerous, and is capable of carrying Kalibr cruise missiles – the Russian equivalent of US Tomahawk missiles. It can also deploy naval mines.

Laid down in August 2010 at Admiralty Shipyards in Saint Petersburg, launched in November 2013, and commissioned on August 22, 2014. It was the first of six Improved Kilo II submarines built specifically for Russia's Black Sea Fleet. Conducted missile tests in the Barents Sea in 2015, including Kalibr launches at the Chizha range. It made a controversial port call in Ceuta, Spain, near Gibraltar, sparking diplomatic tensions.

Deployed multiple times to the Mediterranean in support of Russia's intervention in the Syrian Civil War, including relief rotations at Tartus naval base. In September 2024, it again deployed to the Mediterranean, replacing the submarine Ufa.

In September 2022, amid Ukrainian attacks on Sevastopol during the Russia-Ukraine war, the Black Sea Fleet's Kilo-class submarines—including Novorossiysk—were relocated from Crimea to the more secure Port of Novorossiysk in Krasnodar Krai, Russia. This move was confirmed by the UK Ministry of Defence to protect assets from drone and missile strikes. The port has since faced Ukrainian drone attacks (e.g., in September 2025), though submarine operations continued largely unaffected.

Prior to its sighting near Gibraltar, the Novorossiysk was spotted off the French coast of Brittany in 2022, prompting authorities there to dispatch a vessel to follow it. In July this year, it was spotted again – this time in the English Channel – and was subsequently tailed by the British navy.

Although VChK-OGPU claims the Novorossiysk was on a “combat mission”, it does not necessarily mean it was intending to target British positions on Gibraltar, or anything else for that matter. “Most often, these types of missions are about intelligence gathering or the discreet transport of personnel and equipment," Alexandre Vautravers, a defence expert and editor-in-chief of the Swiss Military Review, said. The Strait of Gibraltar is perfect for these types of covert operations. It is the only maritime gateway between the Atlantic and the Mediterranean, and all vessels passing through it are closely monitored.

On top of that, Russia has a tradition of maintaining a naval presence in the Mediterranean, explained Basil Germond, an international security expert and maritime affairs at Lancaster University. “It’s long-term naval deployments to achieve political, economic and strategic objectives by projecting its military influence in a region,” he said. He described Russia’s ability to exert influence in the Mediterranean as “very limited” at the moment, however, pointing to the war in Ukraine and its recent loss of the naval base in Tartus, Syria. “It was a major setback for the Russian navy,” he said. This meant that the Novorossiysk is likely one of the few Russian warships still operating in the Mediterranean, showcasing Moscow’s waning influential power in the region.

With no official confirmation from the Kremlin, the extent of the reported damage – or whether there is any at all – remained unclear. But in line with VChK-OGPU’s claim that Novorossiysk lacked both spare parts and competent staff to repair the potentially explosive fuel leak, Germond noted that: “Russian warships are known to be poorly maintained, with crews that are untrained to handle these types of situations."

Russia’s war efforts in Ukraine have resulted in even less spare parts and specialised staff being available. Vautravers underscored that the Novorossiysk “is not a nuclear sub. So the environmental and safety impact of an explosion [of the ship itself] would be limited.” The risks, he said, are rather tied to the type of arms that might be onboard. Mines and missiles would make the situation much more dangerous.

Another challenge the crew faces, Germond said, is that Russia has no ports nearby and the Novorossiysk would have to be towed all the way to Saint Petersburg to be repaired. “Considering the current climate, Russia definitely won’t ask a NATO country for help if it isn’t able to resolve the problem by itself,” he said. One of the few remaining solutions, a source told the VChK-OGPU channel, would be for the crew members to “start pumping out the bilge” themselves, into the sea.

October 14, 2025: The Dutch navy confirmed that it escorted the Novorossiysk and an accompanying tugboat, the Yakov Grebelsky, through the North Sea. NATO Secretary General Mark Rutte publicly mocked Russia over the incident, calling it a "broken Russian submarine limping home from patrol" and noting there is "hardly any Russian naval presence in the Mediterranean left." The incident highlighted Russia's declining Mediterranean naval presence after losing full access to its Syrian base at Tartus following the fall of the Assad regime in December 2024. Russian submarines now must make a 4,000 km voyage from the Baltic to operate in the Mediterranean, straining crews and maintenance schedules.

Officials noted that it is highly unusual and strategically disadvantageous for a submarine to remain surfaced for such a long journey. Some analysts have suggested that the vessel's surfaced transit and the presence of a support tug indicate a technical problem.

Russia's Black Sea Fleet denied any malfunction, stating the surfacing was routine and complied with international regulations for transiting the English Channel. Russian state media cited the United Nations Convention on the Law of the Sea (UNCLOS), which requires submarines to pass through international straits on the surface. Some experts acknowledge that the presence of a support tugboat is not unusual for the Russian navy, suggesting that this return trip may have been a pre-planned, routine move.

As of October 15, 2025, the submarine's status remains unclear, with no official Russian confirmation of the event. It was reportedly en route back to Novorossiysk for repairs, highlighting ongoing maintenance challenges for Russia's submarine fleet amid heightened operational tempo.

The Kilo-class remains a backbone of the Russian Navy, with over 60 active units worldwide (including exports to nations like China and India), though newer variants like Project 636.3 are being prioritized for fleets facing modern threats. The Novorossiysk's issues underscore vulnerabilities in diesel-electric subs during extended deployments.