The Moscow office of human rights charity Amnesty International has been sealed off by Russian authorities, according to the charity.
An Amnesty spokesperson told The Independent staff had arrived at work this morning to find the office doors sealed, the locks removed, the electricity cut off and the alarm system de-activated.
Attached to the door was a notice apparently from Moscow city authorities, from whom Amnesty rent the building, saying no one could enter the office without being accompanied by a Russian official. The premises was "property of a city of the Russian Federation", the note said.
However, when staff called the phone number on the notice there was no answer.
Amnesty had no warning of the closure and is still unsure why the office was sealed. Its staff in Moscow are understood to be working to try to resolve the issue as quickly as possible.
It is understood there have been no arrests and the charity does not at this stage believe the office has been searched by authorities.
John Dalhuisen, Amnesty International's Europe Director, said:
"We do not know what prompted the Moscow authorities to prevent our staff from accessing our offices - an unwelcome surprise for which we received no prior warning.
"Given the current climate for civil society work in Russia, there are clearly any number of plausible explanations, but it's too early to draw any conclusions. We are working to resolve the situation as swiftly as possible and very much hope there is a simple administrative explanation for this setback to our work.
"We are 100% confident that we fulfilled all our obligations as tenants."
Amnesty International has been highly critical of Russia in recent years - the latest example of which saw Amnesty demand Russian authorities investigate allegations of torture against a well-known opposition activist - Ildar Dadin - currently in prison.
Dadin, who was jailed for a series of street protests, claims he has been repeatedly beaten and threatened in prison. Russia's prison service have denied the claims but said they will investigate if Dadin compalins formally. Kremlin spokesman Demitry Peskov said the case merited "the closest attention" and that President Vladimir Putin would be informed.
Russian law requires all NGOs receiving overseas funding to register as foreign agents, which brings a nuber of restrictions. Last year, the country passed a law allowing foreign organisations to be banned from the country if they are deemed "undesirable" on national security grounds
As for the apparent sealing of the Amnesty office in Mocow Mr Peskov told reporters on Wednesday that he was unaware of the move.
