Kyiv also said it was behind a drone hit on an oil depot in a Russian border region, as Ukraine flexes its ability to strike Russia from the air and at sea with its troops struggling on the front lines.
The Black Sea has been a vital battleground in the two-year war.
Ukraine claims to have destroyed more than two dozen Russian ships since Moscow invaded in February 2022.
Ukraine's GUR military intelligence unit on Tuesday released a black and white video of what it said was the overnight attack on the Sergei Kotov, a 94-metre (308-foot) Russian military patrol ship.
The footage showed a naval drone approaching the side of the vessel, before a large explosion can be seen sending fire, smoke and debris into the sky.
"Another very successful operation. Great news," said GUR spokesman Andriy Yusov.
The attack happened near the Kerch Strait, off the Crimean peninsula that Moscow annexed in 2014.
Officials in Kyiv revelled in the hit, a much-needed boost for its forces with Moscow in the ascendancy on the battlefield.
"One Russian ship has been upgraded to a submarine," Ukraine's defence ministry said in an ironic post on X.
Delays to Western aid -- a $60-billion US aid package and European artillery shells -- have left Ukraine's troops outnumbered and outgunned across the sprawling front lines.
French President Emmanuel Macron called on Tuesday for Kyiv's allies not to be "cowards" in helping them fight the Russian invasion.
- 'Symbol of occupation' -
There was no official response from Moscow, 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.
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.
Kyiv says it has disabled at least 25 Russian vessels since Moscow invaded -- more than a third its pre-war Black Sea fleet.
"Russia's Black Sea Fleet is a symbol of occupation. It cannot be in Ukrainian Crimea," the Ukrainian president's chief of staff, Andriy Yermak, said on Tuesday.
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.
A Ukrainian intelligence source also told AFP 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 "blast" and "fire at an infrastructure site", without providing further details. Footage posted on social media showed black smoke billowing into the air and at least one tank on fire.
In the neighbouring Kursk region of Russia, authorities said an artillery strike triggered a fire at the Glushkovo railway station and cut off power to a nearby village.
- 'Cowards' -
On the land, Russia's Defence Minister Sergei Shoigu said Tuesday his forces were "continuing to press the enemy westwards", as they seek to advance following the capture of Avdiivka last month.
Meanwhile, Berlin said "individual error" was behind a leak of confidential military talks in which air force officials discussed the potential impact of sending long-range missiles to Ukraine.
Moscow has said the leaked recording showed Ukraine's Western allies were directly involved in the conflict.
France's Macron called Tuesday on Ukraine's Western backers to "live up to history" and show "bravery" in their support for Kyiv.
"We are surely approaching a moment for Europe in which it will be necessary not to be cowards," he said on a visit to the Czech Republic.
He was speaking as the European Union unveiled an ambitious proposal to massively boost weapons production and procurement to reduce its reliance on US arms and as a response to the Russian invasion.
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