MOSCOW: Russian opposition leader Alexei Navalny on Tuesday announced that he would run for president in 2018 after a court victory allowed the outspoken Kremlin critic to be a candidate.

In an email sent to supporters, the 40-year-old anti-corruption campaigner said: "Presidential polls will take place in our country in 2018 and I have decided to take part in them."

President Vladimir Putin has not yet confirmed his candidacy but is widely expected to stand in March 2018 for a fourth term. If he wins, he could rule until 2024, when he would turn 72.

The Levada independent polling agency in November gave Putin an 86 per cent approval rating.

Navalny swept to prominence as a punchy orator at mass protests against Putin's re-election in 2011 and 2012, with slogans such as "Putin is a thief!"

Russia needs to hold elections that are competitive and have a "confrontation of ideas," he said in a campaign video posted on YouTube.

"Those in power have already been there 17 years and have stopped reacting to any criticism."

He vowed to tackle issues including unfair distribution of wealth, selective justice and costly participation in military conflicts, with a particular focus on Russia's rampant corruption.

The lawyer leads a group of anti-corruption whistleblowers that has published embarrassing revelations about state officials luxuriating in vast mansions and flying pets in private jets.

In a campaign video, he asks: "How long will we see ministers who keep suitcases of money at home?" -- an apparent reference to last month's arrest of disgraced economy minister Alexei Ulyukayev on suspicion of taking a $2 million (1.88-million-euro) bribe.

Russia's oil and gas revenues should be used "to create modern infrastructure -- hospitals, schools and roads -- not to build luxurious palaces for officials," he said in his campaign statement.

He also promised to stop Russia "throwing away" money on conflicts in Syria and Ukraine -- where Russia denies its troops have backed pro-Moscow separatists.

Navalny's nationalist views have alienated some liberals and his presidential programme calls for tighter visa controls on migrant workers from ex-Soviet Central Asia.

- Legal ban lifted -

Navalny had been barred from standing for office under Russian law as he was handed a five-year suspended term in 2013 on fraud charges. He and his supporters dismissed the allegations as politically motivated.

But in November Russia's Supreme Court quashed the conviction following a ruling by the European Court of Human Rights that he had not received a fair trial, freeing him up to run.

However, instead of dropping the case entirely, the Supreme Court sent it back for retrial in the provincial city of Kirov and proceedings have already begun in a trial that could see him banned again.

The secretary of the Central Electoral Commission Maya Grishina told RIA Novosti state news agency that Navalny's eligibility to run would "depend on the result of the read judication."

Lawyer Dmitry Agranovsky, who has represented opposition activists, told RIA Novosti that Navalny's chances of standing were "minimal" since he will almost certainly be found guilty again.

Kremlin spokesman Dmitry Peskov declined to comment on Navalny's bid.

Navalny already has experience of campaigning for high office.

He stood for Moscow mayor in 2012 with a Western-style campaign against a Kremlin-backed incumbent and scored a surprise second place with 27 percent of the vote.

His presidential bid was trending on Russian Twitter on Tuesday afternoon and his campaign video had been viewed more than 122,000 times.