Russia’s communications regulator has blocked the website of OVD-Info, a prominent human rights monitor that tracks political persecution and anti-Kremlin protests, the group said on December 25.

OVD-Info, which also provides support to victims of political persecution, said Russian media regulator Roskomnadzor had blocked its website earlier this week.

"At the moment, we have not received a notice and do not know the reason for being blocked," the group said on Twitter.

The Interfax news agency said the ruling on restricting access to the ovdinfo.org site was issued by a court in the Moscow region on December 20.

Russia declared the OVD-Info group a "foreign agent" in September, in a move that critics say is designed to stifle dissent.

OVD-Info co-founder Grigory Okhotin had blasted the move as being part of “the pressure campaign against independent organizations and media.”

Russia’s so-called foreign agent legislation was adopted in 2012 and has been modified repeatedly. It requires nongovernmental organizations that receive foreign assistance, and that the government deems to be engaged in political activity to be registered, to identify themselves as “foreign agents,” and to submit to audits.

Human Rights Watch has condemned Russia’s “foreign agent” laws, calling them “another repressive tool the government can use to harass independent groups.”

Russian authorities have unleashed a sweeping crackdown against opposition activists as well as independent media and rights groups in recent months.

Based on reporting by AFP and Reuters