Top opposition leader Alexei Navalny triumphantly returned home to Russia's capital on Saturday after his unexpected release from prison, saying he would push ahead with a bid to become Moscow mayor.
The chief opponent of President Vladimir Putin stepped off an overnight train from the provincial city of Kirov with his wife Yulia to a crowd of hundreds of supporters chanting his name as dozens of riot police stood watch.
"We are going to run and we will win," Navalny said through a megaphone to roars of approval from the crowd, many of whom clutched flowers and wore white T-shirts reading "Navalny" or "Navalny's brother".
"Ahead of us is a big, difficult electoral campaign. Seven weeks of non-stop work and it's just the start," he said.
Navalny was suddenly released Friday pending an appeal of his five-year sentence on fraud charges and has about a month to campaign, but it is unclear whether he will have enough time to actually participate in the September 8 ballot.
The guilty verdict disqualifies Navalny from politics, and the restriction will come into force if or when the verdict is upheld on appeal.
Although opinion polls say Navalny has almost no chance of beating the incumbent pro-Kremlin mayor in the ballot, observers say campaigning for the high-profile post will boost the charismatic leader's popularity.
"Let's fight for political power in the country," he said, pumping his fist in the air and leading the crowd in a chant of "We are the power" before fans hoisted him on their shoulders.
Navalny's conviction and sentencing to five years in a penal colony by a Kirov court on Thursday sparked protests in Moscow and Saint Petersburg from supporters of the charismatic 37-year-old who led unprecedented demonstrations against Putin in 2011-12.
Police said Saturday that vandalism charges would be pursued against whoever scrawled grafitti such as "Putin is gay" and "Putin is a thief" on the parliament buidling during the rallies.
In an unexpected move less than a day after his sentencing, a higher court in the sleepy industrial city 900 kilometres (560 miles) northeast of Moscow released Navalny from jail pending the appeal.
The court ruled that keeping the father of two behind bars would "limit his right to be elected" in the Moscow mayoral polls, for which he had already registered as a candidate.
Many observers described the surprise release as a sign of infighting among the country's ruling elite and uncertainty about how to handle Putin's popular opponent.
Some analysts have said the jailing of a high-profile Moscow mayoral candidate during the campaign was a huge embarrassment for the authorities.
--- 'They have gone mad' ----
Security at the Yaroslavsky train station in central Moscow was tight with the deployment of dozens of riot police, a move supporters said showed the authorities' fear of the opposition leader.
"They have gone mad," activist Nikolai Lyaskin told AFP aboard the train minutes before it pulled into the station.
Navalny emerged as a key figure in the 2011-12 protests against Putin's return for a third term in the Kremlin.
He has said he wants to run in the next presidential election in 2018 and has vowed to jail Putin if he comes to power.
Navalny was found guilty of defrauding the government in the Kirov region of 16 million rubles ($500,000, 376,000 euros) in a timber deal while acting as an advisor to the local authorities in 2009.
He has said the charges are politically motivated.
An opinion poll said before Navalny's sentencing that incumbent pro-Kremlin mayor Sergei Sobyanin is set to retain the post with 78 percent of the vote, with Navalny expected to come a distant second on eight percent.
But observers say the campaign will provide him with valuable exposure in a country in which the Kremlin keeps tight control over most media.
"Participation in the race for the Moscow mayor, the most prominent elected office in Russia after the presidency, will dramatically elevate Navalny's public profile, irrespective of the outcome," said the Eurasia Group consultancy.
Some experts say his popularity will only grow with his release as he will be seen as a hero standing up to the country's elites, widely considered corrupt.
"Navalny has carte blanche," wrote former lawmaker and liberal commentator Irina Khakamada. "Whatever Navalny does now, he will be in a 'win-win' situation."
Navalny's sentencing prompted concern in the West, with a White House spokesman saying it showed a "disturbing trend of government actions aimed at suppressing dissent in civil society in Russia".