The Russian parliament on Wednesday voted to approve a contentious bill that activists fear will introduce Internet censorship by blacklisting sites deemed as undesirable.

In a further controversial move, deputies also passed in first reading a bill that makes libel and slander criminal offences with punishment of up to five years.

"The goal of the bill is to wipe out dissent in our country," Communist deputy Anatoly Lokot exclaimed at the hearings as other opposition deputies said that restrictive bills are introduced faster than they can read them.

The two bills are criticised as likely to be used against the opposition and follow initiatives hiking protest fines and introducing the term "foreign agents" for NGOs with funding from abroad.

The trend to fast-track certain bills after their introduction by majority party United Russia led some critical lawmakers to compare the parliament to a "secretarial office" of the Kremlin.

The Russian-language version of Wikipedia went on strike the day earlier in protest at the bill that is advertised as a crackdown on child pornography by creating a register of blacklisted sites and obliges site owners and providers to close them.

"Imagine a world without free knowledge," it said, blocking access to the site. The site was back up on Wednesday as deputies passed the bill with next to no debate or public discussion.

"Mind boggling," opposition leader Alexei Navalny wrote on Twitter after even opposition deputies voted to pass the law, calling them "idiots."

In Washington, the US State Department voiced its concerns.

"As Secretary (of State Hillary) Clinton has noted, the Universal Declaration of Human Rights guarantees the right 'to seek, receive and impart information and ideas through any media and regardless of frontiers'," said spokesman Patrick Ventrell.

The bill has to be signed by President Vladimir Putin and is expected to become law in November.

Russian newspapers said Wednesday the final version had narrowed a previously broad term of "harmful information", saying only child pornography, suicide how-to instructions and drugs propaganda can lead to website closure without a trial.

However, an expert on Russia's security services, Andrei Soldatov, said the bill would lead to creation of a mechanism for blocking foreign sites for the first time by forcing Internet providers to install special equipment.

"Clearly, it will be possible to use it not just against websites propagating pornography; the government will be able to use these instruments any way it wants," he wrote on his website Agentura.ru.

Russia's biggest search engine Yandex said the bill's proposed methods to fight pornography "create room for possible misuse and raise questions from Internet users and company representatives."

"Such decisions cannot be taken hastily, the way it is happening now," said the statement signed by the company's chief editor Yelena Kolmanovskaya. The engine's slogan "Everything will be found" had the word 'everything' crossed out on the main page on Wednesday.

"The amendments can lead to introduction of censorship to Russian Internet," said Livejournal, a popular blogging platform frequently used by opposition leaders for communicating with their audience.

The new libel bill breezed through the voting process in the parliament in the first reading and could be passed before the end of this week before the Duma session ends for summer break.

The bill creates a new criminal charge making slander and libel subject to a jail term of up to five years. The charge was previously decriminalised during Dmitry Medvedev's presidency under the drive to liberalise the criminal code.

Opposition deputies on Wednesday decried what they said was a trend of introducing restrictive bills at short notice and ramming them through without any public discussion.

"We are turning the parliament into an secretarial office that carries out somebody else's wishes," opposition deputy Gennady Gudkov of the Just Russia party said at the hearings.