Oleksiy Goncharenko, head of the council of Odesa which houses Ukraine's largest naval base, identified the vessel on his Telegram channel this morning as the Admiral Makarov - a $500million frigate that was only commissioned five years ago.
He said the vessel ran into difficulties overnight, before reposting a report from a local news outlet suggesting it had been shot with a Ukrainian missile near Snake Island - whose defenders memorably told another warship to 'go f*** yourself' .
Unconfirmed reports suggest rescue vessels and aircraft have set off from Russia's largest Black Sea port of Sevastopol towards the site, while flight tracking data shows an American drone circling nearby.
If the Makarov is confirmed as hit, it would be another hugely embarrassing blow for Russia after Ukraine managed to sink the Moskva - the flagship of Putin's Black Sea fleet - last month, with the loss of hundreds of her crew.
Goncharenko, posting to his followers around 10am today, wrote: 'The patrol frigate of the Russian Navy 'Admiral Makarov' is despondent. The God of the seas takes revenge on the offenders of Ukraine.
'The frigate Admiral Makarov was laid down in February 2012 at the Yantar shipyard in Kaliningrad and launched in September 2015.
'And in 2022, when he took part in the murder of Ukrainians, he was struck by the God of the Seas. He hasn't set off after Moskva yet, but the trouble has begun.'
'God of the seas' is likely a reference to Neptune - the name of Ukraine's main anti-ship missile.
Around half an hour later, he posted an article from local news outlet Dumskaya which said: 'According to preliminary information, the frigate was unable to dodge the Ukrainian Neptune anti-ship missile.
'The ship is badly damaged, but remains afloat. For now.'
Nobody from the Ukrainian military has so-far commented on the attack, and there has been no acknowledgement from the Kremlin either.
However, the Ukrainian armed forces did add one boat to its tally of destroyed Russian equipment published today without giving further details.
The Makarov is an Admiral Grigorovich-class frigate, one of the Russian navy's newest vessels and the most state-of-the-art frigate operating in the Black Sea.
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Costing around $500million each, the warships are equipped with eight cruise missile launchers and have almost certainly been involved in attacks on cities in western Ukraine during the conflict.
They also carry a 100mm naval gun, two dozen anti-aircraft missiles, anti-ship torpedoes and close-in weapons systems designed to blow up incoming missiles.
The Admiral Makarov is one of three major naval combatants in the Russian navy in the Black Sea.
It was 'the best and most important of them', according to an analysis by forbes.com in a report earlier today.
'And that makes the 409-foot Admiral Makarov perhaps the most valuable target for Ukrainian missile crews and drone operators.
'We don't know exactly which of its best Neptune anti-ship missiles the Ukrainian navy has left or whether Kyiv's TB-2 drones are hunting for the Russian frigate or her Black Sea sisters.
'In any event, it's apparent Russian fleet commanders appreciate the danger.
'There's evidence Admiral Makarov's skipper has been taking pains to keep her away from the Ukrainian coast.
- Oleksiy Goncharenko, head of Odesa regional council, said Russian frigate Admiral Makarov got into 'trouble' in the Black Sea overnight
- He reposted local news article suggesting it was shot with a Ukrainian missile
- Reports also suggest that Russia has dispatched rescue boats and aircraft, while tracking data shows an American drone circling overhead
- If confirmed, it would be second warship hit after Moskva was sunk last month
Russian warships have generally been keeping their distance from the Ukrainian coast ever since the Moskva was shot and sunk on April 14.
It was initially suggested that Ukraine had used drones to distract the ship before hitting it with two Neptune cruise missiles.
But, based on images of the ship taken as it sank, new analysis suggests that its main radar arrays may not have been active when it was attacked.
Analysts for the United States Naval Institute say the radar dishes on the top of the ship appear to be in a 'stowed' position as the Moskva sinks, which likely means they were not active or not fully active.
That means the vessel's surface-to-air missiles - its main defence against incoming attacks - would not have been fully operational at the time, meaning it would not have been able to see the Ukrainian rockets before they hit.
Ukraine also appears to have targeted the ship's most-vulnerable point, its forward engine room and 'survivability compartment' which distributes power to the ship and runs its damage control systems.
Blowing up this part of the ship could have caused 'a loss of all electrical power,' analysts say, which would have massively hampered the ability of the crew to fight the subsequent fire that broke out.
And US officials have since confirmed that they gave satellite data to Ukraine which it subsequently used to target the ship.
Unnamed officials told American newspapers that Ukraine had asked about a ship sailing to the south of Odesa.
The US said it was the Moskva and helped confirm its location before the attack.
Despite being the most high-profile ship sunk by Ukraine, the Moskva is not the first - that inglorious trophy belongs to the Orsk, a transport ship sunk back in March.
On that occasion, the vessel was struck by Ukrainian rockets after Russian state media propaganda gave away its location at the port of Berdyansk.
A direct hit on the Orsk caused it to catch fire and sink, while two smaller landing craft moored alongside were damaged by managed to sail away.
The Orsk was subsequently scuttled and now sits at the bottom of Berdyansk harbour, making the water too shallow for Russia to use for other ships.