Ukrainian forces said they hit and badly damaged the flagship of Russia’s Black Sea fleet, and Russia said its crew was forced to evacuate as a result of a fire without acknowledging an attack, as the battle shifts east and around the battered city of Mariupol where the defenders were still holding out.

The governor of the Odesa region, Maksym Marchenko, said the Ukrainians struck the guided-missile cruiser Moskva with two missiles and caused “serious damage.”

Russia’s Defense Ministry confirmed the ship was damaged but not that it was hit by Ukraine — it said ammunition on board detonated as a result of a fire of as-yet undetermined causes. The entire crew was evacuated, it added; the cruiser typically has about 500 on board.

If confirmed, the sinking of the cruiser would be a major blow to Russia, after the tank carrier Orsk was hit and set on fire in an attack in Berdyansk in the Sea of Azov late last month.

The reported ship attack by Neptune cruise missiles came a day after President Joe Biden called Russia’s actions in Ukraine “a genocide” and approved $800 million in new military assistance to Kyiv, saying weapons from the West have sustained Ukraine’s fight so far and “we cannot rest now.” The munitions include artillery systems, armored personnel carriers and helicopters.

Russia invaded on Feb. 24 with the goal, according to Western officials, of taking Kyiv, toppling the government and installing a Moscow-friendly replacement. But the ground advance slowly stalled and Russia lost potentially thousands of fighters. The conflict has killed untold numbers of Ukrainian civilians and forced millions more to flee. It also has rattled the world economy, threatened global food supplies and shattered Europe’s post-Cold War balance.

The presidents of Poland, Lithuania, Latvia and Estonia showed their support to Ukraine on a visit Wednesday to war-ravaged areas and demanded accountability for what they called war crimes. They meet with their counterpart, Volodymyr Zelenskyy, and visited Borodyanka, one of the towns near Kyiv where evidence of atrocities was found after Russian troops withdrew to focus on the country’s east.

“There are no doubts that they committed war crimes. And for that, they should be accountable,” Latvian President Egils Levits said.

The Lithuanian president, Gitanas Nauseda, added: “The fight for Europe’s future is happening here.” He called for tougher sanctions, including against Russian oil and gas shipments and all the country’s banks.

In one of the most crucial battles of the war in the southern port city of Mariupol, Russian Defense Ministry spokesman Maj.-Gen. Igor Konashenkov said 1,026 troops from the Ukrainian 36th Marine Brigade surrendered at a metals factory. 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.”

Russian troops are gearing up for a major offensive in the eastern Donbas region, where Moscow-allied separatists and Ukrainian forces have been fighting since 2014. Mariupol is a key piece in the Russian campaign and lies in the Donbas, which the Russians have pummeled for weeks.

It was unclear when a surrender may have occurred or how many forces were still defending Mariupol.

Russian state television broadcast footage Wednesday that it said was from Mariupol showing dozens of men in camouflage walking with their hands up and carrying others on stretchers or in chair holds. One man held a white flag. In the background was a tall industrial building with its windows shattered and roof missing, identified by the broadcaster as the Iliich metalworks.

A U.N. task force warned that the war threatens to devastate the economies of many developing countries that are facing even higher food and energy costs and increasingly difficult financial conditions. U.N. Secretary-General Antonio Guterres said the war is “supercharging” a crisis in food, energy and finance in poorer countries that were already struggling to deal with the COVID-19 pandemic, climate change and a lack of access to funding.

In his nightly address, Zelenskyy noted that the prosecutor of the International Criminal Court visited the Kyiv suburb of Bucha, which was controlled by Russian forces until recently and where evidence of mass killings and more than 400 bodies were found.

“It is inevitable that the Russian troops will be held responsible. We will drag everyone to a tribunal, and not only for what was done in Bucha,” Zelenskyy said late Wednesday.

He also said work was continuing to clear tens of thousands of unexploded shells, mines and trip wires left in northern Ukraine by the departing Russians. He urged people returning to homes to be wary of any unfamiliar objects and report them to police.

Also Wednesday, a report commissioned by the Organization for Security and Cooperation in Europe found “clear patterns of (international humanitarian law) violations by the Russian forces in their conduct of hostilities.” It was written by experts selected by Ukraine and published by the Vienna-based organization, which promotes security and human rights.

The report said there were also violations by Ukraine, but concluded those committed by Russia “are by far larger in scale and nature.”

Russian President Vladimir Putin has denied his troops committed atrocities, saying Tuesday that Moscow “had no other choice” but to invade and would “continue until its full completion and the fulfillment of the tasks that have been set.” He insisted Russia’s campaign was going as planned despite a major withdrawal after its forces failed to take the capital and suffered significant losses.

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Associated Press writer Robert Burns in Washington, and AP journalists around the world contributed to this report.

AP