Ukraine has accused Russian forces of bombing a theatre where civilians were being sheltered in the besieged southern city of Mariupol.
Deputy Mayor Sergei Orlov told the BBC between 1,000 and 1,200 people had sought refuge in the building. The number of casualties is still unknown.
Images of the aftermath of the attack showed extensive damage.
Russia's airstrikes and shells have previously hit a maternity hospital, a church and apartment buildings.
Mariupol's city council said in a statement that Russian forces "deliberately and cynically destroyed" the theatre, saying a "plane dropped a bomb on a building where hundreds of peaceful Mariupol residents were hiding".
The statement said the number of casualties was still not clear because the city continued to be shelled. Pictures of the theatre, which have been verified by the BBC, showed smoke billowing from the site.
Satellite pictures taken on 14 March - released by the US company Maxar - showed the word "children" had been marked on the ground in large letters to warn Russian jets away from the building.
Ukraine's President Volodymyr Zelensky denounced the bombing and said Russia had deliberately targeted the theatre.
"Our hearts are broken by what Russia is doing to our people. To our Mariupol," he said in a video address on Wednesday evening
Both Dmytro Kuleba, the Ukrainian foreign minister, and the city council accused Russia of a "war crime" in the wake of the attack.
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