Ukraine says it just carried out the first-ever underwater drone strike on a Russian submarine

• Ukraine's internal security agency said it used an underwater drone to damage a Russian submarine.
• The agency described the attack as a first, potentially signaling a new chapter in drone warfare.
• Ukraine has long been using naval drones to target Russian surface ships.

Ukraine carried out a first-of-its-kind attack on a Russian submarine using underwater drones, Kyiv said on Monday, revealing a new use for its explosive-packed uncrewed systems.

The Security Service of Ukraine, or SBU, said it executed a "unique special operation" using an underwater drone to strike a Russian Kilo-class submarine at the Black Sea port Novorossiysk, damaging and disabling the boat.

The SBU, Ukraine's main internal security agency, disclosed that the attack involved the employment of its "Sub Sea Baby" drones, which appear to be an underwater version of the Sea Baby naval drone Ukraine uses to target Russian surface vessels and port infrastructure.

The SBU said in a statement that the submarine was equipped with four launchers for Kalibr cruise missiles, which Russia regularly fires at Ukrainian cities.

The security agency did not specify when the operation took place, but it said it was carried out in coordination with the Ukrainian navy. The SBU published footage that appears to show the moment the underwater drone impacted the submarine, causing a large explosion.

Neither Russia's defense ministry nor its US embassy immediately responded to requests for comment.

The Kilo-class submarines are diesel-electric boats that have been in service since the 1980s. Russia has dozens of active subs, which make up one of the largest submarine fleets in the world.

The SBU said a Kilo-class submarine costs around $400 million, but the agency added that sweeping international sanctions would make it notably more costly for Russia to build a replacement.

The submarine attack marks the latest against Russia's naval force in the Black Sea. Since the start of the war, Ukraine has employed drones and missiles to damage and destroy dozens of warships and other vessels.

The asymmetrical campaign has forced Russia to relocate the bulk of its battered Black Sea Fleet from the long-held headquarters on the occupied Crimean peninsula across the region to Novorossiysk. However, Ukraine has demonstrated it can target Russian ships there as well.

The SBU said on Monday that the damaged submarine was in Novorossiysk due to the Ukrainian operations that drove the Russian Navy away from Crimea earlier in the war.

More significantly, the submarine attack appears to signal a new chapter in drone warfare. Ukraine has used naval drones, such as the Sea Baby, to strike Russian surface ships and used underwater drones to target Russia's "shadow fleet" vessels moving oil and circumventing sanctions.

However, a strike on a submarine with what has been likened to a slow-moving mine or torpedo suggests an expansion of Ukrainian capabilities.

Beyond Ukraine, Russia and NATO countries have actively developed their own underwater drone technology as militaries look to augment traditional naval capabilities with more uncrewed systems.