Russian prosecutors searched Amnesty International's Moscow offices on Monday, the latest in a series of raids on advocacy groups that activists say is a new wave of state harassment.
Since returning to the Kremlin in May, President Vladimir Putin has signed laws to tighten controls on non-governmental organizations, requiring those with outside funding to register as "foreign agents."
The Kremlin says the legislation is needed to prevent groups spying for foreign governments, but raids by state authorities ranging from tax officials to fire inspectors are seen by Putin's critics as part of a campaign to stifle dissent.
"It's a sort of harassment," said Sergei Nikitin, Russia director of Amnesty International, a London-based human rights advocacy group. "This inspection was not planned."
The prosecutor's office was not immediately available for comment and it was not clear why Amnesty's offices had been searched.
The United States, the Council of Europe and Amnesty itself expressed alarm last week over the wave of searches including of Russian group Memorial, Russia's oldest rights group.
Amnesty on Friday said the searches "reinforce the menacing atmosphere for civil society" in Russia. The US embassy called them a cause for "great concern," and Europe's commissioner for human rights called for an immediate halt to the raids.
Putin has accused foreign governments, including the United States, of meddling in Russia's domestic politics.
Russia closed the US Agency for International Development's (USAID) operations earlier this year, saying it had tried to influence politics.