Ukraine’s military on Tuesday claimed another successful attack on a Russian warship, marking the latest in a string of naval defeats for Moscow’s Black Sea Fleet that Kyiv says has reduced its numbers by more than a third since the start of the war.

The Defense Intelligence of Ukraine said maritime drones operated by its Group 13 special unit struck and sank the 1,300-ton Russian patrol ship Sergei Kotov in the Black Sea, near the Kerch Strait that separates occupied Crimea from the coast of southwest Russia.

“As a result of the strike by Magura V5 maritime drones, the Russian ship Project 22160 ‘Sergei Kotov’ sustained damage to the stern, starboard and port sides,” sparking a fire aboard the vessel, a statement said. The military later confirmed the ship had sunk.

The mission was conducted in cooperation with the Ukrainian Navy and with the support of Ukraine’s Ministry of Digital Transformation, it added.

Andriy Yusov, representative of the Defense Intelligence of Ukraine, said in an interview with Radio Free Europe/Radio Liberty that the Sergei Kotov had been targeted and hit before, but “this time the Sergei Kotov has been destroyed for sure.”

Seven Russian crew members were killed and six were wounded, the Defense Intelligence of Ukraine claimed on Telegram. It did not reveal how Ukraine had come by this information.

Ukraine’s maritime drones have taken a heavy toll on Russian naval ships, especially in the past few months, with its campaign in the Black Sea a rare strategic success for Kyiv compared to recent setbacks on the battlefield.

In mid-February, the Russian landing ship Caesar Kunikov was attacked with the same drones used against the Sergei Kotov. The drones punctured “critical holes” on the Russian ship’s left side before sinking it, Ukrainian military intelligence agency said on Telegram.

Earlier in February, Ukraine claimed its forces had disabled about 33% of Russia’s warships, amounting to 24 disabled ships and one submarine. Russia’s worst naval loss of the war was the sinking of the guided-missile cruiser Moskva in April 2022.

The Sergei Kotov was one of Russia newest ships in the Black Sea Fleet. A report from Russian state-run news agency TASS on January 21, 2021, said the ship was floated on that day and would soon join the Black Sea Fleet.

The TASS report said the 300-foot-long (91 meters) warship had a range of 6,000 nauticial miles, could carry a crew of 80 and was equipped with a helicopter, a 57mm gun and a modern air defense system. Ukraine said it had a price tag of $65 million.