The Russian missile cruiser that was damaged in a fire on Thursday was hit and ultimately sunk by Ukrainian missile strikes, a senior U.S. defense official confirmed on Friday. Russia and Ukraine had offered differing accounts of what happened to the vessel.

The defense source confirmed the ship was hit by two Neptune missiles, and told NPR there are likely casualties.

Experts say the loss of the Moskva  the flagship of Russia's Black Sea fleet  is significant both symbolically and militarily, even if it doesn't deal a decisive blow to Russia's overall operations.

Russia loses warship, says will increase attacks on Kyiv

Russia's Defense Ministry has said that a fire broke out on board, causing munitions to explode and prompting the evacuation of its crew, which is believed to number about 500. Ukraine claims responsibility, saying it hit the vessel with two Neptune anti-ship missiles about 60 miles off the coast of Odesa.

The defense source confirmed the ship was hit by two Neptune missiles, and told NPR there are "likely casualties."

Russian defense officials said later that the vessel sank while being towed to shore in stormy weather  though weather reports indicate that conditions in the Black Sea were mild.

While losing one vessel isn't going to immobilize the Russian navy, it reinforces the narrative that Ukrainian troops can still deliver powerful blows by being more agile and creative, as NPR's Greg Myre reports. This is the second major vessel Russia has lost off the coast of Ukraine in recent weeks.

The Pentagon previously noted that other Russian warships in the northern Black Sea moved further away from the coast following Thursday's episode, which raised questions about Russia's claim that it was an accident.

A key warship in Russia's fleet was severely damaged. Ukraine claims responsibility

Ret. Admiral James Foggo, who commanded U.S. Naval forces for Europe and Africa, said earlier on Thursday that while the forensics of what happened took time to be determined, the significance of the loss was clear  especially since the flagship of any navy is "the biggest and the best and the brightest."

"This is a terribly humiliating blow to the Russian navy, and it's rather astonishing that they can allow this to happen to themselves," Foggo told Morning Edition.