The Russian Black Fleet flagship, the guided-missile cruiser Moskva, is fighting a fire in the northern Black Sea.
Ukrainian forces claim to have hit the Russian cruiser with a long-range missile. Western officials say there is not yet enough information to attribute the fire to a specific cause, but the damage to the Russian flagship appears extensive and is a blow to Russia's navy.
US officials believe that Moskva has experienced significant damage, but they don't know what caused it, or whether there are casualties.
The Russian ship was hit with Neptune anti-ship missiles. Russian state media said Thursday that the Moskva was afloat, its main armaments were intact, and the fire had been contained to some area but not extinguished.
The US official wouldn't rule out an accident despite the fact that the Russian account of a fire breaking out aboard was difficult to believe.
The risk of fire is always present and the US defense official pointed out that a ship like Moskva is designed for air defense.
This would be the first use of the Neptune missiles. The Neptune can hit land and sea targets within a 200 mile range. It is the first mid-range cruise missile produced by Ukraine and designed to strike warships.
A US official said that the cruiser was between 60 and 65 nautical miles south of Odesa when it experienced an explosion.
The US official said that the fire was "extensive" and " significant" but that it was not clear if there was damage to the hull. The US official said that it was their assumption that the ship would be heading to Sevastopol for repairs.
A US official said that roughly a half-dozen ships were dispersed in the northern Black Sea at the time of the explosion.
At this point, we hold them no closer than 80 nautical miles from the coast, but ships move and I can't predict where they'll be an hour from now.
It has been speculated that Russian commanders are trying to increase the distance between their ships and Ukrainian coastal defenses, which are being strengthened by weaponry provided by Western countries.
The Moskva was involved in the attack on the Snake Island at the start of the Russian invasion. When asked by the Russian fleet to surrender, Ukrainian guards on the island were heard saying "Russian warship, go f--- yourself." Speaking Thursday, the US official couldn't confirm that Moskva had been involved in that incident.
Moskva has been active around Odesa. Russian landing ships have been sent to the port multiple times but have been diverted at the last moment, tying up Ukrainian forces in the area with threats of an assault.
Russia will not be able to reinforce its ships in the Black Sea after Turkey closed the sea to warships at the beginning of the conflict.
It was one of the most severe naval losses since the Falklands War, according to an expert on naval warfare in East Asia.
Russian commanders will feel less secure tonight as they reflect on the fact that the Black Sea is no longer their lake. Patalano said it was a box with no way out.