Russian freedom of speech is "shrinking alarmingly" under President Vladimir Putin, says Amnesty International.

The murders of outspoken journalists go unsolved, independent media outlets have been shut and police have attacked opposition protesters, said the report.

It also said "arbitrary" laws were curbing the right to express opinion and silencing NGOs deemed to be a threat by the authorities.

The report comes ahead of Russian's presidential elections on 2 March.

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The director of Amnesty International UK, Kate Allen, said: "The space for freedom of speech is shrinking alarmingly in Russia and it's now imperative that the Russian authorities reverse this trend."

She said dissent could be a matter of life or death in the case of outspoken journalists like Anna Politkovskaya, who was shot dead in Moscow two years ago.

The 52-page Freedom Limited report warned any opposition demonstrations could suffer heavy clampdowns in the coming days, as Amnesty said had happened in the run-up to past elections.

First Deputy Prime Minister Dmitry Medvedev, whom President Vladimir Putin has named his favoured successor, is expected to be elected in this Sunday's poll.