Attempts to rescue people from underneath a theatre in Mariupol are being hampered by intense fighting in the area, the city’s mayor has said.
Hundreds of people, including women and children, are thought to be trapped after the Drama Theatre was bombed on Wednesday.
Ukrainian officials say Russia attacked the theatre, which was clearly marked as a civilian shelter.
The Kremlin has refuted these claims.
City mayor Vadym Boychenko told the BBC that teams were only able to clear the rubble of the building during breaks from the fighting.
“[There is] street fighting in the city centre,” Mr Boychenko said.
“There are tanks... and artillery shelling, and all kinds of weapons fired in the area.
“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.”
On Friday, the Russian defence ministry said its forces were “tightening the noose” around the city, and that “fighting against nationalists” was taking place in the city centre.
Ukrainian President Volodymyr Zelensky says Russian shelling is still preventing the establishment of effective humanitarian corridors from Mariupol.
Russian troops have have encircled the city, cutting it off from electricity, water or gas.
About 300,000 people are trapped inside the city.
Food and medical supplies are dangerously low, while Ukraine has said Russia is blocking the entry of humanitarian aid.
Russian attacks have hit residential areas including a maternity hospital, a church and residential areas.
Local officials say 80 per cent of apartment blocks are either damaged or destroyed.
Meanwhile, a third are beyond repair.
Mariupol has seen some of the fiercest battles since Russia invaded Ukraine, 24 days ago.
The city is of strategic importance to Russia, as it would help it create a land corridor between the eastern regions of Donetsk and Luhansk, which are controlled by Russian-backed separatists, and Crimea, the peninsula it invaded and annexed in 2014.
