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The Security Service of Ukraine (SBU) reported earlier today that it had carried out a joint operation with the Ukrainian Navy to destroy a Russian Kilo-class (“Varshavyanka”) submarine in the Black Sea port of Novorossiysk. According to the SBU, the submarine was struck by a type of underwater drone known as the Sub Sea Baby, marking the first time such an unmanned system has been used to attack a submarine. The explosion caused critical damage, the agency said, effectively putting the vessel out of action.
The submarine was equipped with four launchers for Kalibr cruise missiles, which Russia has used to strike targets across Ukraine. The operation was conducted by the SBU’s 13th Main Directorate of Military Counterintelligence, together with the Ukrainian Navy.
Russia’s Black Sea Fleet responded by denying the extent of the damage — but not the fact of the attack. The fleet’s press chief, Capt. 1st Rank Alexei Rulev, confirmed to the Ministry of Defense-run Zvezda television channel that an attack had taken place, but stated that “the attempt at sabotage did not achieve its objectives.”
“None of the ships or submarines of the Black Sea Fleet stationed in the bay of the Novorossiysk naval base, nor their crews, were damaged as a result of the sabotage and are continuing to serve as usual,” Rulev said.
The SBU estimated the cost of a Varshavyanka-class submarine at about $400 million, adding that, given international sanctions, building a comparable vessel today could cost up to $500 million. The class is also known by the unofficial nickname “Black Hole” because of its low acoustic signature, which makes it difficult to detect by sonar.
Project 636.3 Varshavyanka submarines — known in NATO classification as Improved Kilo — are third-generation diesel-electric submarines and are considered to be among the quietest in the world. They are about 74 meters (243 feet) long, displace roughly 3,900 tons of water, and have a maximum diving depth of 300 meters (about 980 feet). Six such submarines were originally built for Russia’s Black Sea Fleet, but after the start of Moscow’s full-scale invasion of Ukraine, several have been damaged or destroyed by Ukrainian strikes. One of them, the Rostov-on-Don, was hit in a dry dock in Sevastopol in September 2023.
The SBU said the submarine targeted in the most recent strike had been forced to remain in Novorossiysk because earlier attacks by Sea Baby surface drones successfully drove Russian warships and submarines out of Russian-occupied Sevastopol.