The Internet must be subject to reasonable regulation, the head of Russia's Security Council said in remarks published on Wednesday, a fresh sign of Kremlin concern about the use of social networks to promote anti-government protests.

Opposition groups and ordinary Russians used Facebook and the Russian site VKontakte to organize protests last week over a December 4 parliamentary election they charged was rigged to benefit Prime Minister Vladimir Putin's ruling party.

Tens of thousands of people rallied on Saturday in the biggest anti-government protests since Putin came to power 12 years ago, many chanting Russia without Putin!

Opponents plan further protests ahead of a March election expected to return Putin, a former Soviet KGB officer and Russian Federal Security Service (FSB) chief, to the presidency.

Attempts to stop people from communicating are in principle counterproductive and even amoral, Security Council secretary Nikolai Patrushev, who headed the FSB during Putin's 2000-2008 presidency, told the daily Argumenty i Fakty.

However, one must not ignore the use of the Internet by criminals and terrorist groups. Reasonable regulation, of course, must be conducted in Russia, as is done in the United States, China, and many other countries, he said.

Chinese government controls on the Internet are far stricter than those in the United States, and Patrushev gave no details in the newspaper interview, but his remarks suggest Russian authorities are considering ways of reining in the Internet.

Putin has publicly said that the state's ability and right to control Internet use is limited, and suggested his government would not try to do so. Analysts say hardliners close to Putin would like to impose controls similar to China's.

Vkontakte, Russia's top social networking site, said last week that it had rejected a request by the FSB to block opposition groups from using it to organize street protests.

A spokesman for VKontakte, used by tens of thousands of people to coordinate support for the December 10 protests, said the company was not pressured or threatened.

Ahead of the parliamentary vote, however, the websites of the independent election monitoring group Golos and at least two media outlets that had aired reports of alleged campaign violations were blocked by denial-of-service attacks.

The head of Golos, a Western-funded group that has a site with a map showing reported cases of electoral violations, said she suspected the FSB was behind the attacks.

Russian officials have expressed concern about the powerful role of online communication in the unrest that has brought down governments in the Arab world in the past year.

A senior FSB officer said in April that uncontrolled use of Gmail, Hotmail and Skype were a major threat to national security.

(Editing by Rosalind Russell)

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