Alexei Navalny, Russia's most prominent opposition figure, has been detained by police and charged with unlawfully organizing a public gathering.
Navalny has called for demonstrators to protest Saturday outside the mayor's office against the rejection of several opposition candidates from the ballot for this fall's Moscow city council elections.
In a short video on social media, Navalny said he was seized by police outside his home on Wednesday morning as he went out for a run and to buy flowers for his wife's birthday. His lawyer Olga Mikhailova told the Interfax news agency that Navalny had been charged with organizing an unauthorized gathering.
Conviction could carry a penalty of 30 days in jail and a fine of up to 300,000 rubles ($4,600).
After the candidates for city council were rejected on the grounds of invalid signatures on their nominating positions, protesters held an unsanctioned demonstration outside the city election commission.
Russia's Investigative Committee on Wednesday said it was opening a criminal case over that demonstration, although potential charges were not specified.
The head of the voters' rights committee of the Presidential Human Rights Council, Ilya Shablinsky, was quoted by Interfax as saying the move was "complete nonsense ... This whole chain of actions by the authorities means that real competition is not allowed."
The latest crackdown on Russia's opposition politicians came as they fight to get on the ballot for the Moscow parliament elections in September amid falling approval ratings for President Vladimir Putin.
They have however been disqualified on what critics say are spurious grounds.
Putin's top opponent Navalny and other anti-Kremlin politicians threatened to stage a major rally on July 27, near the mayor's office, unless Moscow authorities registered opposition candidates.
- NEW PROBE -
Investigators also opened a criminal case into obstructing the work of election officials after Navalny's allies and ordinary Muscovites staged a series of pickets and rallies outside the offices of the Moscow election commission and elsewhere.
For that offence organisers could face up to five years in prison.
Investigators said they would "question the organisers and participants of unauthorised rallies and pickets."
The protests involved "threats to use violence against members of the electoral commissions", the Investigative Committee said.
This month Navalny already served a 10-day jail sentence for violating a protest law.
Navalny's arrest came after more than 22,000 people rallied in Moscow last Saturday to demand independent politicians be allowed to run in the September 8 vote.
The opposition said Saturday's authorised protest was the largest since 2012, when tens of thousands rallied against election fraud during parliamentary polls.
The opposition politicians have worked hard to get on the ballot paper as they seek to capitalise on anger over declining living standards and unchecked corruption.
They say they were made to jump through countless hoops, and each had to collect roughly 5,000 signatures to be eligible.
But electoral authorities still refused to register the representatives of the opposition, accusing them of faking some of the signatures.
- 'CITY HALL IS AFRAID' -
The Kremlin dismissed the opposition's complaints but many Russians are furious at what they perceive as electoral interference.
After the protest, 17 independent candidates including Ilya Yashin and Lyubov Sobol issued a joint statement, accusing Moscow mayor Sergei Sobyanin of sparking a "political crisis" in the city of some 15 million people.
On Tuesday, the disqualified politicians met with the country's election chief, Ella Pamfilova, who admitted that the situation was "unfair".
The talks however led nowhere, the opposition said.
Yashin, who is a local councillor, expressed hope that Navalny's arrest would mobilise people.
"Just think about it: a mere demand to put representatives of the opposition on the ballot papers triggers a use of force scenario," Yashin said on Facebook.
Another independent would-be candidate, Konstantin Jankauskas, said the crackdown was an attempt to discourage people from attending the Saturday rally.
"It means City Hall is afraid that a lot of people would turn up," he said on Twitter.
Political commentator Alexander Kynev said the authorities would seek to nip in the bud the new protest wave by launching a crackdown.
"If this does not help and a lot of people turn up on Saturday then they'll think what to do next," he told AFP.
