Armed with tape and scissors, Alexei Orlov attached some cardboard on a wall outside a residential building known as the "Writers' House" in Moscow.

The bespectacled history buff was putting up cards honouring the victims of Stalinism to replace the metal plaques that started disappearing.

"Here lived Stanislaw Ryszard Stande, a Polish poet born in 1897, arrested in 1937, executed on 1.11.1937, rehabilitated in 1955," read the card.

Two other plaques commemorating the memory of Soviet writers executed in 1938 and 1952 have been mysteriously removed from the wall.

"The plaques are taken away without us knowing why or by whom," said 56-year-old Orlov.

The plaques were put up with the consent of a building's current residents to commemorate previous inhabitants who were killed under Stalin.

The project was launched in 2014 by the "Last Address" foundation to honour the victims of Stalin's repression that killed millions.

But the "Last Address" foundation estimated that around 200 of the 1,300 plaques have been taken down by vandals.