KYIV, Ukraine (AP) – The flagship of Russia’s Black Sea fleet, a guided-missile cruiser that became a potent target of Ukrainian defiance in the opening days of the war, sank Thursday after it was heavily damaged in the latest setback for Moscow’s invasion.

Ukrainian officials said their forces hit the vessel with missiles, while Russia acknowledged a fire aboard the Moskva but no attack. U.S. and other Western officials could not confirm what caused the blaze.

The loss of the warship named for the Russian capital is a devastating symbolic defeat for Moscow as its troops regroup for a renewed offensive in eastern Ukraine after retreating from much of the north, including the capital.

The Russian Defense Ministry said the ship sank in a storm while being towed to a port. Russia earlier said the flames on the ship, which would typically have 500 sailors on board, forced the entire crew to evacuate. It later said the blaze had been contained and that the ship would be towed to port with its missile launchers intact.

The ship can carry 16 long-range cruise missiles, and its removal from combat reduces Russia’s firepower in the Black Sea. It’s also a blow to Russian prestige in a war already widely seen as a historic blunder. Now entering its eighth week, Russia’s invasion has stalled because of resistance from Ukrainian fighters bolstered by weapons and other aid sent by Western nations.

The news of the flagship’s damage overshadowed Russian claims of advances in the southern port city of Mariupol, where they have been battling the Ukrainians since the early days of the invasion in some of the heaviest fighting of the war – at a horrific cost to civilians.

Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov said Wednesday that 1,026 Ukrainian troops surrendered at a metals factory in the city. But Vadym Denysenko, adviser to Ukraine’s interior minister, rejected the claim, telling Current Time TV that “the battle over the seaport is still ongoing today.”

It was unclear how many forces were still defending Mariupol.

Russian state television broadcast footage that it said was from Mariupol showing dozens of men in camouflage walking with their hands up and carrying others on stretchers. One man held a white flag.

Mariupol’s capture is critical for Russia because it would allow its forces in the south, which came up through the annexed Crimean Peninsula, to fully link up with troops in the eastern Donbas region, Ukraine’s industrial heartland and the target of the coming offensive.

The Russian military continues to move helicopters and other equipment together for such a effort, according to a senior U.S. defense official, and it will likely add more ground combat units “over coming days.” But it’s still unclear when Russia could launch a bigger offensive in the Donbas.

Moscow-backed separatists have been battling Ukraine in the Donbas since 2014, the same year Russia seized Crimea. Russia has recognized the independence of the rebel regions in the Donbas.

The loss of the Moskva could delay any new, wide-ranging offensive.

Maksym Marchenko, the governor of the Odesa region, across the Black Sea to the northwest of Sevastopol, said the Ukrainians struck the ship with two Neptune missiles and caused “serious damage.”

Oleksiy Arestovych, an adviser to Ukraine’s president, called it an event of “colossal significance.”

Russia’s Defense Ministry said ammunition on board detonated as a result of a fire, without saying what caused the blaze. It said the “main missile weapons” were not damaged. In addition to the cruise missiles, the warship also had air-defense missiles and other guns.

The Neptune is an anti-ship missile that was recently developed by Ukraine and based on an earlier Soviet design. The launchers are mounted on trucks stationed near the coast, and, according to the Washington-based Center for Strategic and International Studies, the missiles can hit targets up to 280 kilometers (175 miles) away. That would have put the Moskva within range, based on where the fire began.

The U.S. was not able to confirm Ukraine’s claims of striking the warship, U.S. national security adviser Jake Sullivan said Thursday. Still, he called it “a big blow to Russia.”

“They’ve had to kind of choose between two stories: One story is that it was just incompetence, and the other was that they came under attack, and neither is a particular the good outcome for them,” Sullivan told the Economic Club of Washington.

During the first days of the war, The Moskva was reportedly the warship that called on Ukrainian soldiers stationed on Snake Island in the Black Sea to surrender in a standoff. In a widely circulated recording, the soldier responds: “Russian warship, go (expletive) yourself.”

The AP could not independently verify the incident, but Ukraine and its supporters consider it an iconic moment of defiance. The country recently unveiled a postage stamp commemorating it.

Russia invaded on Feb. 24 and has lost potentially thousands of fighters. The conflict has killed untold numbers of Ukrainian civilians and forced millions more to flee.

It’s also further inflated prices at grocery stores and gasoline pumps because Ukraine and Russia are major producers of crops and energy, while dragging on the global economy. The head of the International Monetary Fund said Thursday that the war helped push the organization to downgrade economic forecasts for 143 countries.

Also Thursday, Russian authorities accused Ukraine of sending two low-flying military helicopters across the border and firing on residential buildings in the village of Klimovo in Russia’s Bryansk region, some 11 kilometers (7 miles) from the frontier. Russia’s Investigative Committee said seven people, including a toddler, were wounded.

Russia’s state security service had earlier said Ukrainian forces fired mortar rounds at a border post in Bryansk as refugees were crossing, forcing them to flee.

The reports could not be independently verified. Earlier this month, Ukrainian security officials denied that Kyiv was behind an air strike on an oil depot in the Russian city of Belgorod, some 55 kilometers (35 miles) from the border.


Associated Press journalists around the world contributed to this report.