Sobol has avoided arrest until now because she has a five-year-old daughter and Russian law states that no one can be arrested on administrative charges if they have a dependent minor.
Despite repeated warnings that police would take active measures against a protest on Saturday, activists aimed to hold a march for about four kilometres along the Boulevard Ring that circles central Moscow and is a popular area to stroll.
Alexander Svidersky, a member of a district electoral commission, said he was arrested while out with his dog, which he managed to pass off to an acquaintance before being bundled into a police van.
Media Zona, a Russian media outlet, shared a video footage by Znak.com news organisation on Twitter, saying police were beating protesters who were lying on the ground. Sobol was one of more than 600 arrested in Saturday's protests, according to an independent monitoring agency.
"They are going into the crowd and detaining people".
Protestors insist their actions are strictly peaceful, and there have been no reports of damaged property.
"They (the authorities) are wiping their feet on us", said Elena, a student attending Saturday's protest.
The dispute over the local election has provoked a large outcry.
The local issue has boiled over into one of the worst political conflicts of recent years, with rallies of up to 22,000 people and police violence against demonstrators.
Authorities launched the clampdown as opposition politicians are fighting to get on the ballot for a Moscow parliament election in September amid anger over worsening living standards and President Vladimir Putin's falling approval ratings.
"I believe everyone should have a right to take part" in the polls", 39-year-old Robert said.
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The Moscow city council, which has 45 seats, is responsible for a large municipal budget and is now controlled by the pro-Kremlin United Russia party.
The dispute comes as the Kremlin is struggling with how to deal with strongly opposing views in its own sprawling capital of 12.6 million people.
Protesters have been gathering in central Moscow for weeks to protest the Moscow Election Commission's rejection of independent candidates on the September 8 ballot for Moscow's Duma, a 45-seat body that oversees the capital's multimillion-dollar budget.
Lyubov Sobol, one of the excluded candidates and a driving figure of the current wave of protests, was among those detained on Saturday She was grabbed by police in central Moscow and hustled into a police van, loudly demanding to know why she was being held.
To create "an impression of lawful possession and use" of criminal money, "the co-conspirators deposited the sum through Moscow's ATMs to accounts at several banks", the committee's spokeswoman Svetlana Petrenko said, adding that the cash was transferred to the accounts of the FBK afterwards. Navalny's ally Leonid Volkov dismissed allegations of money laundering as an attempt to stamp out Navalny's national network of volunteers. She has been on hunger strike for 21 days, and called on others to join the unsanctioned protest on Saturday. Last weekend he was hospitalized with what he and his team suspect was poisoning, though officials have said his toxicology tests showed no trace of poison.