KYIV, April 14 - 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 two Ukrainian-made Neptune anti-ship missiles late Wednesday, while Russia only acknowledged a fire aboard the Moskva but no attack.

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, Kyiv.

The elimination of Moskva opens significant opportunities for Ukraine to launch an operation targeting Russian troops in southern regions, such as Kherson and Crimea. Moskva had 64 advanced S-300 anti-aircraft missiles denying Ukrainian aircraft from accessing the airspace in the region.

The ship also had the capacity to carry 16 long-range cruise missiles, and its removal 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 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 aboard, forced the entire crew to evacuate. Later it said the blaze had been contained.

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.”

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 it was when the fire began.

Launched as the Slava in 1979, the cruiser saw service in the Cold War and during conflicts in Georgia and Syria, and helped conduct peacetime scientific research with the United States. During the Cold War, it carried nuclear weapons.

In 1989, the Slava was supposed to host a meeting off Malta between Soviet leader Mikhail Gorbachev and U.S. President George H.W. Bush, but gale-force winds moved the talks to the docked cruiser Maxim Gorky.

On Thursday, other Russian ships that were also in the northern Black Sea moved further south after the Moskva caught fire, said a senior U.S. defense official who spoke on condition of anonymity to discuss internal military assessments.

Before the Moskva sank, Yuriy Sak, an adviser to Ukraine’s defense minister, told The Associated Press its removal would mean “ we can only have a sigh of relief because this means that fewer missiles will reach Ukrainian cities.”

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.”

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, a soldier responded: “Russian warship, go (expletive) yourself.” (ap/ez)