Russia's media watchdog Roskomnadzor has contacted Facebook, Google and Twitter and warned the firms that if they do not fully comply with Russia's internet laws they may be blocked.

A Roskomnadzor spokesperson commented, "In our letters we regularly remind (companies) of the consequences of violating the legislation."

The organisation says that encryption technology used by the companies does not allow the government to block specific sites that carry content which violates Russian laws, so they might block all their services.

The main issue is a demand from Roskomnadzor that says that it must be given access to information about Russian bloggers with over 3,000 readers per day, as it cracks down on sites containing what the spokesman describes as the promotion of "unsanctioned protests and unrest."

Russian President, Vladimir Putin has said that it is not his intention to put the internet under full government control, but many worry that this kind of interference with the spreading of political ideas online represents an attack on free speech.

Amnesty International's most recent review of Russian human rights comments, "the Kremlin has strengthened its grip on the media and the internet, clamped down on protest and harassed and demonised independent NGOs."

It adds that in 2014, "public protests took place, but participants risked fines and detention. The freedom of the media shrank and the internet was subjected to ever greater restrictions; social networks and blogs were often restricted and internet-based resources blocked by court."

Laws passed last year give the government the power to block websites promoting unauthorised protests without going through the court system.

Legislation requires bloggers with large followings to go though an official Government registration process.