The Moscow office of human rights group Amnesty International has been officially sealed up overnight by Russian authorities.

Sergey Nikitin, the head of Amnesty International in Russia, says when employees "arrived at our office this morning, they found that the door was broken and there were new locks." Photographs on Wednesday showed the door sealed up with an official notice from Moscow city authorities.

Nikitin said International Amnesty has rented the office from the Moscow city government for over 20 years.

Human rights organizations in Russia have complained of official pressure in recent years, including the intimidation of their staff and controversial legislation regulating the operation of non-governmental organizations.