16 April 2013 Last updated at 10:40 ET

Profile: Russian opposition leader Alexei Navalny

Mr Navalny is seen here in his office in Moscow on 15 April

Russian anti-corruption campaigner Alexei Navalny, 36, has emerged as the informal leader of the opposition to President Vladimir Putin.

He has become a threat to the Russian political establishment, says the BBC's Moscow correspondent Daniel Sandford.

He has hit them where it hurts, by exposing the extraordinary levels of corruption in their ranks. He has written about it with savage ferocity laced with poisonous sarcasm, our correspondent says.

It is a position, he argues, that has earned him a campaign of persecution by the Kremlin and its allies, including prosecution in the courts on what he says are trumped-up charges.

No stranger to police custody for his role in demonstrations against ballot-rigging, he now faces a possible prison term on fraud charges during a trial in the Russian region of Kirov.

It would be a major blow to an opposition which for years suffered the lack of a central figure or platform.

Nonetheless, Mr Navalny is not without his critics in the anti-Putin camp, not least for what some see as his flirtation with Russian nationalism.

Taxpayer's champion

Disgusted with parliamentary and presidential elections they saw as rigged, the opposition elected their own leaders in October 2012.

Mr Navalny won the most votes in the three-day ballot, which was conducted online and open to the public.

Alexei Navalny basics

• Born 4 June 1976 at Butyn, in the Moscow region
• Graduated in law at Moscow's Friendship of the Peoples University in 1998
• Became a Yale World Fellow in 2010
• Lives in Moscow with his wife and two children

The turnout was small: just 81,801 people voted, fewer than had attended the mass anti-Putin rallies in Moscow Mr Navalny had inspired the previous winter.

But the lawyer from Moscow secured a clear lead over other candidates such as veteran Putin critic and former chess champion Garry Kasparov.

His rise as a force in Russian politics began in 2008 when he started blogging about allegations of malpractice and corruption at some of Russia's big state-controlled corporations.

One of his tactics was to become a minority shareholder in major oil companies, banks, and ministries, and to ask awkward questions about holes in state finances.

Speaking to BBC News this week, he suggested the best thing Western states could do for justice in Russia was to crack down on "dirty money".

"I want people involved in corruption and persecution of activists to be barred from entering these countries, to be denied visas," he said.

"They steal billions, put people in prison and then drink coffee in the streets of Paris and London. The West should put a barrier in the way of dirty money and people who bring it."

'Crooks and thieves'

The campaign against corruption took Mr Navalny from criticism of corporations directly to opposition to the ruling party, United Russia.

Ahead of the 2011 parliamentary election, which he did not fight as a candidate, he urged his blog readers to vote for any party except United Russia, which he memorably dubbed the "party of crooks and thieves".

Mr Navalny is shown here being marched off a by a policeman in Moscow in March 2012

United Russia won the election, but with a much reduced majority, and its victory was tarnished by widespread allegations of vote-rigging that prompted mass protests in Moscow and some other major cities.

Mr Navalny was arrested and imprisoned for 15 days following the first protest on 5 December but emerged to speak at the biggest of the post-election rallies in Moscow on 24 December, attended by as many as 120,000 people.

"I see enough people here to take the Kremlin and [Government House] right now but we are peaceful people and won't do that just yet," the fiery rhetorician told the crowd.

However, Mr Putin later won re-election as president easily and, as he settled back in at the Kremlin, Russia's powerful Investigative Committee launched criminal investigations into Mr Navalny's past activities, even questioning his credentials as a lawyer.

Besides the case before a court in Kirov, three other fraud cases have been opened against him, all of which he says are fabricated:

• he is accused of defrauding a now-defunct liberal political party of 100m roubles (£2m; 2.4m euros; $3.2m) six years ago

• he is accused of embezzling 55m roubles in 2008-11 while working in a postal business with his brother

• he is charged with embezzlement over a timber deal in 2009 in Russia's Kirov region

Before the opening of the Kirov trial, Mr Navalny told BBC News that President Putin had resorted to repressing the opposition because of his own declining popularity, and the decline of the economic boom that has sustained his success.

"It is important for the Kremlin to launch a case of this nature against me, despite the fact that is blatantly fabricated," he said.

"If you put an anti-corruption activist into prison for participating in a political manifestation, it will only help his publicity, but if you say that he is also corrupt..."

Shortly before he was due to go on trial, he announced in a Russian internet TV interview that he planned to run for president. His priorities, he told Dozhd, would be to help people who "have oil and gas running out of the ground not to live in poverty" and "live a normal life like in a European country".

However, Mr Navalny's actual political views are hard to pin down.

The fact he is a Yale World Fellow, following a semester he spent there in 2010, has been regarded with suspicion by Russian nationalists, wary of US influence.

At the same time, his readiness to speak at ultra-nationalist events and his hard-hitting anti-corruption campaigns such as "Stop Feeding the Caucasus" have caused concern among liberals.

The blogger's appeal to the broader Russian population, outside Moscow and the big urban centres, remains a matter of conjecture.