The Russian version of Wikipedia went black on Tuesday to protest against a proposed law that could become the basis for Internet censorship.

Wikipedia's protest is backed by other large Russian online businesses such as the social networking site VKontakte and the Russian LiveJournal.

"We are protesting because the proposed amendments are too inaccurate, and in its current form they can damage Internet development in Russia," said Vladimir Medeyko, director of the Russian Wikimedia foundation, via instant message.

If the new law, "On Information, Information Technologies and Protection of Information," is adopted with the proposed amendments, this might lead to the creation of a Russian analogue of "the great Chinese firewall" or an "electronic curtain," Medeyko said, adding that in a worst-case scenario access to Wikipedia might be blocked in Russia.

Visitors to the Russian Wikipedia site were unable to access it on July 10. Those who tried to access the site saw a black censorship banner over the Cyrillic word for Wikipedia. "Imagine a world without free knowledge," the slogan reads on the blocked website.

Wikipedia is protesting because the State Duma, the Russian lower house of parliament, has proposed to block websites containing illegal content through IP and DNS blockades. Medeyko said that the IT industry in Russia instead proposed blocks on a URL level, but legislators ignored the suggestion.

Using the proposed way to block illegal content could be risky for innocent users, Medeyko said. "If there's just a single violating comment in a blog, the whole blog-service could be blocked," he said.

Russia already experienced the consequences of such a blockade when a court decided that one illegal YouTube video was sufficient to block the entire YouTube.com domain, he said. But that was a decision by the court, and under the proposed amendment, the number of authorities that may forbid access to a site increase. As a consequence, the risk that entire sites may be blocked in the way YouTube was also rises, Medeyko said.

Wikipedia asked visitors to support the protest by sending a message addressed to the Chairman of the State Duma, Sergey Naryshkin. The prefabricated message calls on Naryshkin and the rest of the Duma to discuss the bill in open public hearings with experts on civil society and e-democracy, including representatives from the Internet industry and service providers. The protesters are also asking the Duma to change the proposed blocking process.

The Russian protest against online censorship is similar to U.S. protests against the Stop Online Piracy Act (SOPA) last January, when English version of Wikipedia along with sites as Reddit an Craigslist opposed the legislation by blocking access to their websites.

However, the Russian protest is not as big because it had to be staged in a hurry, Medeyko said. The first reading of the law occurred Friday and the second one is planned for Wednesday, he said, adding that a Russian bill becomes law after the third reading.

The Russian IT industry was not expecting that amendments with such a big impact on the law could be be approved so fast, Medeyko said, adding that sometimes a law can pass through the Duma in one day, but that is an exception and happens when parties agree on the amendments.

Wikipedia is backed by the Russian version of LiveJournal, which protested in a blog post, and Bash.im, the Russian version of quotation site Bash.org, which posted a red banner on each page.

Russian social networking site VKontakte, which has about 290 million users, also joined the bandwagon when the site's founder, Pavel Durov, announced support of the protest.

"We're starting with a banner in all pages. There is a reading of Internet censorship introducing law currently in the Russian Duma. Details at ru.wikipedia.org," Durov announced on Twitter.

Loek covers all things tech for the IDG News Service. Follow him on Twitter at @loekessers or email tips and comments to loek_essers@idg.com