Anti-corruption campaigner Alexei Navalny has cemented his status as leader of Russias opposition movement by organising the largest unauthorised protest in recent years against President Vladimir Putins rule.

The clean-cut lawyer, 40, who was arrested at Sunday's demonstration in Moscow, is no stranger to clashes with the Kremlin.

He has spent time under house arrest and seen his brother jailed in a string of cases he has denounced as retribution for his challenging authorities and exposing the vast wealth of the president's inner circle.

Late last year, in his most ambitious move yet, he announced he would run for president in 2018, an election that Putin is expected to dominate.

This month he posted a YouTube video tracing Prime Minister Dmitry Medvedev's links to mansions, yachts and vineyards that has been viewed 12 million times.

No official response followed, and Navalny called supporters to protest across Russia. Thousands turned out in Moscow, where some 1,000 people were arrested including Navalny.

He now faces up to 15 days in police cells, according to OVD-Info, a website that monitors the detention of activists

In February Navalny was found guilty in a retrial of an embezzlement case that could mean he is not eligible to stand for president -- though he insists he will not be forced out of the race.

Though criticised by some liberals for his anti-immigrant nationalist stance, Navalny has tapped into discontent among the young urban middle class with fiery speeches and Western-style campaigning.

"I will discuss what everyone has been silent about but has needed to be said for a long time," Navalny said in December when announcing his bid for the presidency.

But in an environment where the media and the political landscape are tightly controlled by the Kremlin, he remains a fringe figure for most Russians, who are more likely to believe the official portrayal of him as a Western stooge and convicted criminal.

"Navalny is a unique politician of the younger generation," said Nikolai Petrov, a professor at the Higher School of Economics in Moscow, adding that he had managed to develop a high profile "at a time when public politics has ceased to exist."

Protests and payback

During the mass protests of 2011, sparked by allegations of vote rigging in parliamentary polls, Navalny grabbed attention with his uncompromising rhetoric.

In front of crowds of tens of thousands, he coined catchy phrases such as the "party of crooks and thieves" to slam the governing United Russia.

Although the protests petered out after a crackdown by the authorities and Putin sailed to a third term in March 2012, they helped launch Navalny's political career.

In 2013 he ran a crowd-funded campaign to be mayor of Moscow and ended up finishing second behind the Kremlin candidate, with over 27 percent of the vote.

But Navalny was also facing a series of legal cases against him, a campaign that supporters saw as a sign the Kremlin was running scared.

In July 2013 he was found guilty in an embezzlement case involving an allegedly crooked timber deal and given a five-year suspended sentence.

Navalny was then forced to spend months under house arrest and often kept incommunicado over another graft case linked to the French cosmetics company Yves Rocher.

He was also given a suspended sentence in that case, but his brother Oleg, a co-defendant was jailed for three and a half years.

Palaces and pooches

Despite his travails, Navalny has kept trying to expose the lavish wealth of the elites of the Putin era, broadcasting the findings of his investigations to his 1.8 million Twitter followers.

Trawling through land registries and the filings of offshore companies, Navalny and his team have helped lay bare the hidden fortunes of high-ranking officials.

Among his most eye-catching exposes have been details on the palatial homes of Putin's allies in Russia and abroad -- including one kitted out with a vast storage room for fur coats built by Vladimir Yakunin, former chief of Russia's national railways.

In July 2016, as Western sanctions over Russia's role in the Ukraine crisis and low oil prices hit average Russians hard, Navalny revealed that deputy prime minister Igor Shuvalov was sending his pet corgis on private jets to dog shows around Europe.

"Dear friends, those who voted for Putin and United Russia, you made it possible for Russian officials to steal completely openly and live as they do," Navalny said in an online video.

"Please don't ever do this again."