Navalny was detained outside his home an hour before the rally was to start. "The United States will monitor this situation, and we call on the government of Russian Federation to immediately release all peaceful protesters".
"After trying to intimidate protesters into abstaining from these demonstrations with blackmail and harassment, the authorities in Moscow, St Petersburg and elsewhere have punished hundreds of those who turned up with beatings and arrests", said Denis Krivosheev, Deputy Director for Europe and Central Asia at Amnesty International. "We are calling for all peaceful protesters swept up in these arrests to be immediately freed".
Protests against corruption that were organized by opposition activist Alexei Navalny and his supporters took place in many Russian cities on June 12.
Navalny, who had a green liquid thrown in his face in April, robbing him of some of his sight, said hundreds of people had attended demonstrations in Russia's Far East on Monday morning. The demonstrators are demanding an end to corruption they say is endemic among government officials.
As of early evening, almost 700 people had been detained in Moscow and as many as 900 in St Petersburg, according to rights groups.
According to correspondents, among the protesters many young people who except Putin, other leaders, and not seen, but they are still too small across the country, where about 80% of the population incumbent President support.
Navalny, who is running what he says is a campaign for Russia's presidential elections in 2018, has attracted a substantial following online through his exposés of official graft, using his own YouTube channel to circumvent official state media from which he is effectively barred.
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Why was Alexey Navalny arrested?
Riot police in St. Petersburg have begun detaining demonstrators in an unsanctioned opposition rally in the center of the city. "We left the Pushkinskaya metro station and after five minutes the riot police ran up to us and dragged us to the police bus, which after a few minutes was already crowded with people", the 18-year-old told CNN via text message.
Mr Navalny angered officials in Moscow after he made a last-minute decision to change the main protest's location to one of the city's busiest thoroughfares.
Tens of thousands of people still took to the streets, and more than 1,500 were arrested.
Navalny brought thousands onto the streets across Russian Federation in March, the largest such protests since a wave of anti-Kremlin demonstrations in 2012.
Russian opposition leader is seen getting into a police vehicle as he was detained in front of his home on Monday. He said interference had prevented contractors from building a stage at the agreed venue.
At a midnight court hearing, a Russian judge later found Navalny guilty of repeatedly violating the law on organizing public meetings and sentenced him to 30 days in prison.
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There was also a large police presence in St. Petersburg, where protesters chanted "shame" during a rally at the Field of Mars park.
"The rally is absolutely peaceful, it isn't a protest, just a gathering of people who want to express their views", said Anastasia Lukanina, 30. "Alexei has been detained in the stairwell".
The demonstrations were a follow-up to large-scale protests that swept Russian Federation in late March.
A protestor being led away by the police on Monday summed it up.
In Moscow, thousands of angry protesters held an unsanctioned rally on Tverskaya, the capital's main street.
"Alexei was detained at the entrance of the house", his wife, Julia Bulk, wrote on Navalny's Twitter feed.
The protest was called over government plans to demolish Soviet-era apartment blocks in the city.
Darjeeling unrest: Protestors, police clash
According to the police, the GJM supporter who died during the clashes became the victim of firing from the supporters only. The incident, in which several people were injured , prompted the administration to deploy Army contingents in the area.