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 foe of President Vladimir Putin stepped off an overnight train from the northeastern 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 loudspeaker 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, referring to the September 8 poll.
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.
"Together we are a huge powerful force and I am glad we have started realising this," he said.
"Let's fight for political power in the country," he said, pumping his fist into the air and leading the crowd into 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 2011-2012.
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 his appeal of the conviction.
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.
The release shocked Moscow, with many observers describing it 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 ahead of Navalny's arrival, a move supporters said showed the authorities' fear of the popular 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 2011-2012 protests ahead of Putin's return for a third term in the Kremlin, with his sometimes volcanic rhetoric inspiring supporters in a way never seen before in post-Soviet Russia.
A lawyer by training, he had built up a huge Internet following with sharply-written blogs and corruption exposes and coined the term "the party of swindlers and thieves," for the pro-Kremlin United Russia party.
He has said that he wants to run in the next presidential election in 2018 and has vowed to jail Putin if he comes to power.
In the Kirov case, he 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.
The guilty verdict disqualified Navalny from politics, but the restriction will come into force only if the verdict is upheld on appeal.
He has said the charges were politically motivated.
An opinion poll by the independent Levada Centre said before Navalny's sentencing that incumbent mayor and loyal Kremlin lieutenant Sergei Sobyanin is set to retain the post with 78 percent, with Navalny expected to come second on 8 percent.
But observers say the campaign will provide him with valuable exposure in a country where Kremlin keeps tight control of 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 Eurasia Group consultants.
Some experts say that 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's sentencing also 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."