VINNYTSIA, Ukraine — Ukrainian underwater drones struck a Russian submarine for the first time Monday, causing critical damage to the vessel and making it the first publicly acknowledged use of the new class of Ukrainian weapons, according to Ukraine’s domestic intelligence agency.

At the time of the attack, the Kilo-class submarine was docked in a Russian Black Sea port near the city of Novorossiysk and carried four launchers for Kalibr cruise missiles, which Moscow regularly uses to attack across Ukraine, the agency said. Kilo-class vessels are not nuclear-powered and do not carry nuclear-armed ballistic missiles.

Russia confirmed the attack but denied that its submarine had been damaged.

Ukraine Says It’s Prepared to Continue War

The Ukrainians said the operation had been conducted by the security service in cooperation with the navy, on a day when Ukrainian President Volodymyr Zelenskyy met with U.S. negotiators and European leaders in Berlin to discuss peace proposals. The strike appeared intended to bolster Zelenskyy’s argument that Ukraine can continue to fight back and pose a threat to Russia’s superior forces if no agreement is reached.

“Today, achieving results on the front line is crucial so that Ukraine can achieve results in diplomacy,” Zelenskyy said Friday while visiting Ukrainian positions near the northern front-line town of Kupiansk, where Ukraine said its forces had 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.”

The security service said the drones involved were of a type called Sub Sea Baby, but provided no more details about them. Ukraine has been developing a fleet of unmanned, miniature submarines ranging from about 1 foot to more than 1 yard in diameter. The weapons are essentially long-range torpedoes, looking like black cylinders with fins, some capable of traveling hundreds of miles.

Overnight Monday, Ukraine also carried out a large-scale aerial drone operation targeting a gas processing plant in Russia, according to the Ukrainian armed forces. Despite a series of operations that are seen as intended to strengthen Ukraine’s position at the negotiating table, the country continues to face a difficult situation on the battlefield, remaining largely on the defensive against a Russian offensive that is making small, daily advances along parts of the front line.

Ukrainian Drones Effective Against Russian Navy

Drone operations, nevertheless, have emerged as one of Ukraine’s most effective tools during the war. Using drones, Ukraine has pushed Russia’s Black Sea Fleet largely out of open waters, forcing many vessels to remain in port, and has launched increasingly successful attacks on Russian oil refineries and the “shadow fleet” of oil tankers that Russia uses to evade Western sanctions.

While Ukraine claimed the strike Monday was the first time it had struck a submarine with sea drones, it was not Ukraine’s first attack on a Russian submarine. Ukraine previously struck another Kilo-class submarine, the Rostov-on-Don, twice with missiles while it was docked in Crimean ports — first in September 2023 and again in August 2024. It said the vessel had been damaged beyond repair.

This article originally appeared in The New York Times.

By Maria Varenikova

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