A law that allows authorities to take websites offline and force them to close has come into effect in Russia.
The legislation was passed by the Russian Parliament and signed off by President Vladimir Putin in July.
The Russian government had said the law is to protect children from harmful online content but human rights groups say that it will enable further censorship and the stifling of dissent.
Russia is already heavily criticised for its levels of press and internet freedom
Reporters Without Borders (RWB) expressed grave concern over the development in a press statement: “We are forced to conclude that no political will exists to resolve the law’s contradictions and to eliminate those that pose threats to freedom, despite criticism of the law from many quarters."
Yuri Vdovin, vice-president of Citizens' Watch, told the BBC that to close a website, the government would simply have to say that its content was "harmful to children".
"The government will start closing other sites - any democracy-oriented sites are at risk of being taken offline.
"It will be [an attack on] the freedom of speech on the internet."
A full list of blacklisted sites will be updated daily by the Roskomnadzor (Russia's Federal Service for Supervision in Telecommunications, Information Technology and Mass Communications). It is not available for the public to view.
The new law coincides with a new treason bill that expands the scope of certain terms and imposes harsh sentences on those who are judged to have threatened "foreign security".
The notion of "security" has been widened to include security against domestic as well as foreign threats.
"High treason" has been expanded to include the passing of information, to "international organisations". The new definition includes all “financial aid, technical assistance, consultative or other assistance” provided for “activities directed against the security of the Russian Federation.”
RWB continued:“Now that every Russian NGO receiving foreign financing is required under penalty of imprisonment to label itself a “foreign agent,” the vaguely worded expansion of the ‘high treason’ definition raises deep concern.”
The implication of this is that anyone who shares information with a foreign NGO or even someone who appeals to the European court of human rights, could face a long prison sentence.RWB said: “Taken as a whole, the latest legislative initiatives in the Duma give all the appearance of a concerted attack on freedom to disseminate information."