Efforts are underway to rescue hundreds of people trapped in the basement of a bombed theatre in the Mariupol.
But the city’s mayor says it’s a difficult task, as intense fighting continues nearby.
Ukrainian officials say Russia attacked the site, which was clearly marked as a civilian shelter.
Russian forces have surrounded the city, which has no electricity, water or gas.
300,000 people are still trapped inside.
“[There is] street fighting in the city centre,” Mr Boychenko said, confirming a claim made by Russia on Friday, when it said it was “tightening the noose” around the city.
“There are tanks… and artillery shelling, and all kinds of weapons fired in the area,” the mayor said. “Our forces are doing everything they can to hold their positions in the city but the forces of the enemy are larger than ours, unfortunately.”
A place for children
Satellite images showed the Russian word for “children” had been emblazoned on the ground in two locations outside the imposing Soviet-era building, indicating the place was being used as a civilian shelter.
The authorities in Mariupol say at least 2,500 people have been killed in the city since the start of the war, although they acknowledge that is an underestimate.
