Russian authorities have started destroying the ruined theatre in Mariupol, according to an aide to the city's exiled Ukrainian mayor.

Petro Andryushchenko accused the occupying authorities of seeking to cover up the murder of hundreds of civilians when the building was bombed by Russian warplanes in March.

A screen was recently erected around the ruined theatre.

Video showed a bulldozer knocking down some of the rear of the building.

Mr Andryushchenko said the Russians were planning to leave the front of the theatre intact and destroy the rest of the structure, to build a new theatre "on the bones of Mariupol's people".

A screen was erected around the ruins of the theatre last month, complete with images of Russian cultural figures.

Before Russia invaded Ukraine last February and laid siege to Mariupol, the theatre was a focal point of city life.

This year, Russia's proxy authority that runs the city and the occupied areas of the surrounding Donetsk region has promised the city's remaining population alternative entertainment - a revival of a 1960s Soviet cult musical, The Bremen Town Musicians.

Instead of taking place at the bombed out theatre, it is being staged more than a kilometre away at the Pioneers' Palace.

It is all a far cry from the glitzy new year celebrations held in Mariupol a year ago.

Earlier this month journalists from the Associated Press used satellite imagery to estimate that 10,300 new graves had been dug at a Mariupol cemetery.

The BBC reported in November that witnesses had seen Russian authorities removing bodies from the rubble of destroyed buildings and taking them away for burial. Ukrainian officials believe 25,000 people lost their lives in fighting in the city.

It took months for Russia to win the siege of Mariupol in May, when hundreds of Ukrainian fighters finally surrendered at the city's Azovstal steel plant.

Two months earlier, at around 10:00 on 16 March, Russian warplanes dropped two 500kg bombs on the city's theatre which detonated simultaneously, according to a report by Amnesty International, which condemned the attack as a clear war crime.

Civilians had been using the building as a refuge from the siege and a large sign spelling "children" had been daubed in Russian in front of the theatre.

Some 1,200 people were inside the building when the bombs struck. Ukrainian authorities believe 300 people were killed but an AP investigation said the number was closer to 600. Many of the bodies were found in the basement.