Russia's lower house of parliament approved a law on Wednesday that the opposition says could be used to censor the Internet and crack down on one of the last forums of open political debate under President Vladimir Putin.
His United Russia party said the law, passed in the third and final reading by the State Duma, is needed to combat child pornography. It will create a single register of websites containing information deemed harmful or illegal from November 1.
But the new law has caused alarm among the opposition: Opposition leaders said the new law could be used to shut down websites such as Facebook and Twitter without a court order and that it was meant to stymie their protest movement, which uses social network sites to arrange anti-Putin demonstrations.
Russian search engine Yandex on Wednesday displayed a link to a statement saying the bill needed to be discussed with Internet experts.
"The proposed methods of child protection allow for potential misuse and raise numerous questions from Internet users and companies," said Ochir Mandzhikov, a Yandex spokesman.
"In a bill like this, it is necessary to maintain the balance of public interests while taking into account the technological aspects of the Internet," he said in an e-mail.
The official blacklist is intended to include domains of web pages containing pornographic images of children, instructions on how to make, use and where to get drugs, as well as sites calling for suicides and describing suicide methods.
Under the law, which was softened slightly following criticism, more sites may be added to the list based on either a court decision or with the approval of authorized federal executive bodies.
Communications Minister Nikolai Nikiforov told a news conference that the law needed more work but should not interfere with freedom of information.
"We support the idea of the law as a whole in what concerns the need to provide the means for fighting phenomena such as child pornography. At the same time, we find that the proposed mechanisms are not entirely complete," he said.
"The fight against child pornography must not create problems with the main principle of the Internet - open access to information," he added.
United Russia, which proposed the bill, dismissed criticism of the law as "groundless".