The following are some facts about the Moskva, the Soviet-era flagship of Russia's Black Sea fleet, which sank on Thursday after a fire according to the Russian Defence Ministry. Ukraine said the fire was caused by its missile strike.
EXTENT OF DAMAGE
The defence ministry, cited by Russian news agencies, acknowledged that the ship suffered serious damage, saying that there was a fire from "a detonation of ammunition" and that the vessel sank in stormy seas while it was being towed back to port. Kyiv says the ship started to sink after the fire broke out.
The ship was thought to be located in the Black Sea somewhere off the Ukrainian port of Odesa at the time of the explosion.
Whatever the cause, the episode is a setback for Russia. If Ukraine's assertion that it hit the ship in a missile strike turns out to be true, the attack will go down in history as one of the highest-profile naval attacks so far this century.
The Moskva would be the biggest Russian warship damaged by enemy fire since 1941, when German dive bombers crippled the Soviet battleship Marat in Kronshtadt harbour, military analysts said.
If the damage was caused by some kind of an onboard explosion, it would be the second flagship of Russia's Black Sea Fleet to be taken out of action in a similar fashion. The Imperatritsa Maria dreadnought battleship sank in 1916 after an explosion involving ammunition.
Experts do not see the Moskva's loss as likely to have a major impact on what Russia calls its "special operation" to demilitarise Ukraine.
"The ship is really very old. Actually, there have been plans to scrap it for five years now," Russian military analyst Alexander Khramchikhin said.
"It has more status value than real combat value, and in general, had nothing to do with the current operation. It will have no effect on the course of hostilities."
Russia has sufficient resources to maintain a blockade of Ukrainian ports and to hit targets inside Ukraine with other missile systems, the experts said.
The ship is armed with multiple anti-ship and surface-to-air missiles. Russia has two other ships of the same class, the Marshal Ustinov and the Varyag, which serve with Russia's Northern and Pacific fleets respectively.
The ships were designed in the Soviet Union in the late 1970s to counter U.S. aircraft carrier groups and to provide air defence to Soviet vessels operating in distant oceans. They were nicknamed "carrier killers" at the time.
The Moskva first entered service with the Soviet navy in 1983 after being built in then-Soviet Ukraine and was called "Slava" or "Glory" at the time. It was renamed Moskva (Moscow) in 1995 after the fall of the Soviet Union.
The ship provided security for a meeting of Soviet leader Mikhail Gorbachev and U.S. President George Bush in Malta in December 1989.
Russian President Vladimir Putin has also held meetings on board with world leaders.
The Moskva briefly took part in a blockade of the Ukrainian navy in March 2014 as part of Russia's annexation of Crimea.
In 2015, it took part in Russia's military operation in Syria, providing air defence for Russian forces there.
(Reporting by Reuters correspondents and Ronald Popeski; editing by Grant McCool)