A Russian missile strike on a museum in the eastern Ukrainian city of Kupyansk killed at least one person and wounded 10 others, an attack that President Volodymyr Zelenskiy described as "barbaric," as heavy fighting for the control of Bakhmut intensified over the past day, the military reported.
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Oleh Synehubov, the head of the Kharkiv Regional Military Administration, told RFE/RL that the April 25 strike on the Kupyansk city center involved S-300-type missiles, one of which hit the Museum of Local History.
Synehubov said rescue work continues, with officials saying at least one more person may be under the rubble.
"The terrorist country is doing everything to destroy us completely. Our history, our culture, our people. Killing Ukrainians with absolutely barbaric methods," Zelenskiy wrote on Telegram, adding, "We must and will respond!"
Meanwhile, the Ukrainian military said Russian forces unleashed more waves of assaults on Bakhmut over the past day, but neither side managed to make critical advances in the monthslong battle for the city in the eastern region of Donetsk.
"Fierce battles are going on for the city of Bakhmut," the General Staff of the Armed Forces of Ukraine said in its daily report on April 25, adding that Moscow's main push on the battlefield remained focused on the Bakhmut-Avdiyivka-Maryinka front line.
Russian forces launched 62 air strikes and six missile strikes against Ukrainian military positions and civilian objectives, the General Staff said in its report.
IN PHOTOS: As heavy fighting for control of the shattered city of Bakhmut in eastern Ukraine continues unabated, one Ukrainian unit explains how it is struggling to hold off Moscow's forces.
'We're Tired': Ukraine's Exhausted Forces Hold Their Positions In The Battlefield City Of Bakhmut
Ukrainian defenders also repelled 43 Russian attacks on Bakhmut and Maryinka, the report said.
Ukrainian Deputy Defense Minister Hanna Malyar, meanwhile, described the ongoing fighting in Bakhmut as a "continuous dynamic process."
Malyar said on Telegram on April 25: "We can lose positions in battle today, and regain them the next day; that is why the military prefers to talk about the result after the operation is over."
Malyar's comments came a day after Ukrainian commanders denied a Russian claim that mercenaries from the Wagner Group almost completely controlled the city.
In Washington, National Security Council spokesman John Kirby warned that Russian forces can step up their offensive actions once the weather begins to get warmer.
"We know that in the spring, when the weather improves -- and it is already starting to improve -- we can expect that the Russians will want to go on the offensive in some areas. We don't know exactly where and how they will do it, but we want to be sure that Ukrainians are able to defend themselves better against it," Kirby told Voice of America on April 24.
At the same time, Kirby added, if Ukrainian forces decide to conduct their own counteroffensive operations, they must have the appropriate capabilities.
Military experts have reported -- and Ukrainian leaders have hinted -- that a major spring counteroffensive by Ukraine is in the works.
Russian state news agency RIA said on April 25 that Moscow has begun using its new T-14 Armata battle tanks in the war, firing on Ukrainian positions but not yet participating in a "direct assault."
The tank has an unmanned turret that a crew controls remotely from "an isolated armored capsule located in the front of the hull," the report said.
But, according to British military intelligence, Russian forces have complained about the poor condition of the first of the tanks to arrive.
"Eleven years in development, the program has been dogged with delays, reduction in planned fleet size, and reports of manufacturing problems," the British intelligence report said.
Off the battlefield, the International Working Group on Russian Sanctions, a pro-Ukraine group of scholars, called on Western nations to impose stricter sanctions on Moscow.
The scholars called for a reduction on the price cap on Russian oil to $30 a barrel from $60; a total embargo on Russian steel, iron, and diamonds; and an easing of regulations to seize Russian assets abroad.
The group consists of some 40 scholars -- including Michael McFaul of Stanford University and a former U.S. ambassador to Russia.