The Black Sea has been a vital battleground since the war started just over three years ago.
Ukrainian forces claim to have destroyed more than two dozen Russian ships since Moscow invaded in February 2022, including several in recent weeks.
Ukraine’s GUR military intelligence unit on Tuesday released a black and white video showing what it said was the overnight attack.
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The footage showed a naval drone approaching the side of the Sergei Kotov – a 94-metre (308-foot) Russian military patrol boat – before a large explosion can be seen sending fire, smoke and debris into the sky above the vessel.
Ukraine’s navy said explosive-packed drones had hit the ship near the Kerch Strait off the Crimean peninsula, causing “damage to the stern, starboard and port sides”.
“As for the crew, the details are being clarified. There are dead and wounded. But it is likely that some of the crew managed to evacuate,” military intelligence spokesman Andriy Yusov told local media.
There was no official response from the Russian defence ministry, but Russian military bloggers with close ties to the armed forces confirmed the strike.
Some were scornful of the Russian navy’s inability to defend itself.
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Pro-war Russian military blogger Yuri Podolyak on Tuesday accused Moscow’s military leaders of being in “ostrich mode” – having their heads buried in the sand – over yet another successful Ukrainian attack in the Black Sea.
The Dva Mayora Telegram channel said the crew had been evacuated and survived, though some were injured.
The ship, which was launched in 2021, had already been severely damaged in a strike last year, Ukraine’s Yusov said.
Ukraine’s navy said it was “one of the most modern” vessels in the Russian fleet.
Kyiv has claimed a string of successes in the Black Sea, at a time when its army, faced with ammunition and manpower shortages, is struggling on land.
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It says it has disabled at least 25 Russian vessels since Moscow invaded – more than a third of the pre-war Black Sea fleet.
The Ukrainian president’s chief of staff, Andriy Yermak, said on Tuesday the fleet was “a symbol of the occupation” and “cannot be in Ukraine’s Crimea”.
Moscow has moved many military ships from its historic Sevastopol naval base in Crimea to the port of Novorossiysk, further to the east, amid the spate of Ukrainian attacks.
Kyiv has also successfully opened an alternative grain corridor that allows ships to export Ukraine’s vital agricultural supplies by hugging the Ukrainian coast instead of sailing across the open waters of the Black Sea, which have been packed with mines.
President Volodymyr Zelensky said this week that almost 30 million tonnes of cargo had been exported via the coast route.
A Ukrainian intelligence source also said its forces were behind a drone strike on an oil depot in the Russian border region of Belgorod on Tuesday that set storage tanks ablaze.
The Russian governor had previously reported a “fire at an infrastructure site”, without providing further details.
In the neighbouring Kursk region of Russia, authorities said a strike on the Glushkovo railway station had triggered a fire, cutting off power to a nearby village.
Meanwhile, Ukraine’s air force said it had downed 18 of the 22 Iranian-designed attack drones launched by Russia over the Black Sea port city of Odesa.