A protester holds a placard reading "Putin - No!" during an opposition rally in central Moscow, on 10 March

A law introducing new controls on the internet has come into force in Russia amid concerns it may be used by the government to silence its critics.

In theory, the “sovereign internet” law gives officials wide-ranging powers to restrict traffic on the Russian web.

The Kremlin has said the law will improve cyber security. A spokesman said users would not notice any change.

Critics fear the Kremlin will try to create an internet firewall similar to that in China.

Experts say it is unclear how the powers of the law might be used, or how effectively they can be implemented given the technology challenges and high costs.

What’s the law about?

It gives the Kremlin the possibility to switch off connections within Russia or completely to the worldwide web “in an emergency”. It is up to the government to decide what constitutes a threat and what actions should be taken.

The law requires internet service providers to install network equipment capable of identifying the source of traffic and filter content. In practice, this will allow the telecommunications watchdog Roskomnadzor to be more effective at blocking sites.

  • WATCH: Is the internet encouraging rebellion in Russia?
  • Artists on Russia’s culture, identity and censorship

Russia is seeking to route the country’s web traffic and data through state-controlled points, reducing reliance on foreign servers over which it has less control. Supporters say this is to protect the system from attacks from abroad.

To help with this project, the country is working on developing its own net address books so it can operate almost autonomously, although this work will not take effect until 2021.

Media captionHow Russia wants to control the internet

US intelligence has said Russia used the internet to interfere in the US 2016 presidential election, an allegation Moscow denies.

This is the latest in a swathe of tougher internet laws approved by Russia. Earlier this year, parliament passed two bills outlawing “disrespect” of authorities and the spread of what the government deemed to be “fake news”.

Why are there concerns?

Campaigners say the law is an attempt to increase censorship, building on the internet legislation that already curtails freedom of expression and privacy.

“Now the government can directly censor content or even turn Russia’s internet into a closed system without telling the public what they are doing or why,” said Rachel Denber, Human Rights Watch’s deputy Europe and Central Asia director.

The law, observers say, allows the government to block content without judicial consent and leaves users unaware about what information is being blocked and why.

Christian Mihr, from the group Reporters Without Borders, said: “[The law] proves that the Russian leadership is ready to bring the entire network infrastructure under political control in order to cut off the digital information flow whenever needed.”

In March, thousands of people protested in the capital, Moscow, against the law.

[“source=bbc”]