Mariupol, a strategic port on the Azov Sea, has seen the greatest damage of any Ukrainian city since Russia invaded last month.  Mariupol’s city council said that Russian forces on Saturday bombed an art school where about 400 residents had taken shelter.

There was no immediate word of casualties from the attack on Saturday, although the council said the building was destroyed and there were victims under the rubble.

Volodymyr Zelensky, the Ukrainian president, in his nightly address to the nation on Saturday, described the Russian onslaught on the city as a “terror that will be remembered for centuries to come”.

Authorities in Russian-occupied Crimea, which appeared to be the primary destination for Mariupol residents evacuated from the city, said on Sunday they had received over 11,000 people in the past four days.