The Mariupol city council, which shared an image of the destroyed building, said Russian forces had “willfully and cynically destroyed the drama theater in the heart of Mariupol”.
“The plane dropped a bomb on a building where hundreds of peaceful residents of Mariupol were hiding,” he added.
CNN geotagged the image and confirmed it to be the theater in the southeastern port city.
Videos of the aftermath showed a fire raging through the ruins of the theater. The number of victims is unknown, authorities said.
“It is still impossible to estimate the scale of this horrific and inhumane act, as the city continues to bombard residential areas,” the council wrote on Telegram. “It is known that after the bombing, the central part of the drama theater was destroyed and the entrance to the bomb shelter in the building was destroyed,” he added.
Petro Andruishchenko, adviser to the mayor of Mariupol, described the theater as the largest shelter “in number and size” in the city center. “According to preliminary data, more than a thousand people were hiding there,” he said. “The likelihood of getting there to dismantle the rubble is low due to the constant shelling and shelling of the city.”
The city has no power, water or food, with residents melting snow or dismantling heating systems for a drop to drink, he said on Tuesday.
The attack on the theater comes just a day after a Ukrainian official accused Russian troops of holding some 400 people captive at the Mariupol regional intensive care hospital.
“It is impossible to find words that could describe the level of cruelty and cynicism with which the Russian occupiers are destroying the civilian population of the Ukrainian city by the sea. Women, children and the elderly remain in the crosshairs of the enemy. peaceful and unarmed people,” the city council said.
“We will never forgive and never forget,” he added.
The unfolding humanitarian disaster has enraged the local authorities. “These bastards are trying [to] physically destroy Mariupol and the people of Mariupol, who have been a symbol of our resistance,” Pavlo Kyrylenko, head of administration of the Donetsk region, said on Facebook on Wednesday.
He says “the fate is unknown” of the hundreds of people taking shelter in the theater “because the entrance to the air-raid shelter is blocked by rubble,” he said.
“The Russians are already lying, [saying] that the headquarters of the Azov regiment was located there. But they themselves are well aware that there were only civilians,” he said.
After Russia bombed a maternity ward on March 9, its Foreign Minister Sergei Lavrov alleged without evidence that the hospital was the base of the ultra-nationalist Azov militia battalion and that all the patients and nurses had left.
A Russian Defense Ministry spokesman later denied in a briefing that Russia had bombed the maternity ward, calling it a “provocation”.
Mariupol has been reduced to a combat zone, with the city’s deputy mayor telling CNN on Tuesday that Russia bombed the city with missiles, saying it had 22 planes Monday “bombing our city, and in minus 100 bombs”.
Residents who fled the town described conditions there as “unbearable” and “just hell”. On Tuesday, shocking drone footage and satellite photos emerged showing plumes of thick smoke and destroyed buildings, highlighting the devastation wrought by the Russian bombardment.
As many as 2,500 civilians have died in Mariupol, Ukrainian officials estimate, and hundreds of thousands of people are trapped in the city – with officials warning those left without electricity, water and heating.
CNN’s Ivana Kottasová, Jack Guy and Paul P. Murphy contributed to this article.