Russian authorities in the occupied Ukrainian city of Mariupol have begun demolishing most of the city's drama theatre, where Ukrainian authorities say hundreds died in an air bombardment in March.

Video posted on both Ukrainian and Russian websites on Friday showed heavy equipment taking down much of the building, while leaving its front facade intact.

Ukrainian officials denounced the demolition as a bid to cover up the deaths in the March 16 bombardment and wipe out Ukrainian culture. Russian officials said it was part of plans to rebuild the theatre in a city firmly under their control.

"The Mariupol Theatre no longer exists," Ukrainian Culture Minister Oleksandr Tkachenko wrote on Facebook.

"The occupiers are removing traces of their crimes and couldn't care less whether this is cultural heritage or whether it belongs to another culture."

Russia's Tass news agency quoted the theatre's director, Igor Solonin, as saying that the demolition concerned "only that part of the building that is impossible to restore". Plans called for reconstruction to be complete by the end of 2024.

The bombing of the theatre was part of a protracted Russian siege of Mariupol, a port on the Sea of Azov seen as critical to Russian supply lines between areas its forces control in southern and eastern Ukraine.

Civilians had taken refuge in the theatre and large signs emblazoned simply with "Children" had been erected on either side of it. Ukrainian officials said at least 300 people were killed during the Russian bombing, though some estimates said the toll was higher.

Russia denied bombing the theatre deliberately.

Mariupol held out for more than two months out against Russian assaults which left most of its buildings in ruins.

Petro Andryushchenko, an advisor to the exiled mayor of Mariupol, said that despite demolition, the truth about the theatre bombing "will not stay hidden no matter what they do. There is enough video evidence, witness testimonies and those who survived."

(Reporting by Ron Popeski and Bogdan Kochubey; Editing by Sandra Maler)