Human Rights Watch on Thursday condemned the Russian authorities under President Vladimir Putin for unleashing the toughest crackdown against civil society since the fall of the Soviet Union in 1991.
The repressions against critics come after Putin returned to the Kremlin for a third term in May in the face of unprecedented protests against his 13-year rule.
The crackdown caps a decade of "soft" authoritarianism and opens a new era where Kremlin critics and rights activists are openly harassed and freedoms further eroded, the New York-based group said.
"The Kremlin in 2012 unleashed the worst political crackdown in Russia's post-Soviet history," the watchdog said in a statement accompanying the release of its annual world report.
"Measures to intimidate critics and restrict Russia's vibrant civil society have reached unprecedented levels," the rights group quoted Hugh Williamson, its Europe and Central Asia director, as saying.
Speaking to reporters, his deputy Rachel Denber pointed to an "atmosphere of fear, paranoia and hostility to civil society."
After returning to the Kremlin for a third term despite huge protests against his decade-old rule, Putin signed off on a raft of laws in what critics saw as a bid to quash dissent.
The new legislation re-criminalised slander, raised fines for misdemeanours at protests, expanded the definition of treason and forced non-governmental organisations that receive foreign funding to carry a "foreign agent" tag in a move seen as a throwback to Soviet times.
Human Rights Watch gave a scathing assessment of Putin's Kremlin predecessor Dmitry Medvedev, calling his much-touted efforts at modernisation "few, timid advances on political freedoms."
Anger over fraudulent December 4 parliamentary elections coupled with Putin's September announcement to seek the presidency brought up to 120,000 into the streets of Moscow at the height of winter protests but the momentum has since died down.
Over a dozen activists are now facing jail for taking part in May 6 protests on the eve of Putin's inauguration and for alleged plans to overthrow the Russian strongman with the help of foreign sponsors.
The hopes of political reforms following the anti-Kremlin protests proved short-lived, Human Rights Watch said.
Citing examples of rights violations, the group noted that Alexander Bastrykin, the head of the increasingly powerful Investigative Committee, did not lose his job even after he took the deputy editor of the opposition newspaper Novaya Gazeta to a forest and threatened his life.
Last year the group's own employees were harassed.
Its Russia researcher Tanya Lokshina told reporters last October when she was nearly seven months pregnant that she was receiving text messages with threats to her and her unborn baby.
Lokshina said at the time she might have been under surveillance, pointing to the possible involvement of state security services.
Putin has accused his domestic critics of being in the pay of foreign governments and appears increasingly unwilling to tolerate any international criticism.
The rights watchdog called on Russia's partners not to turn a blind eye to rights violations.
"Russia's civil society is standing strong but with the space around it shrinking rapidly, it needs support now more than ever," Williamson said.
"Russia's international partners should not be bullied into silence."
Moscow's ratification of the UN Convention on the Rights of Persons with Disabilities was a rare boost to human rights, the watchdog said but noted that many disabled people in the country were still denied basic rights.
Asked to comment on the report, Alexander Lukashevich, a spokesman for the foreign ministry, pointed to abuses in the United States and Europe and added that Russia's critics were not "perfect" too.