The majority of the protests planned for Sunday have not been sanctioned by authorities, meaning those who turn up could face arrest. Demonstrators were also arrested in more than 30 other cities, the monitor said.
Mr Putin's trust rating in public opinion polls dropped notably after the proposal was put forward and last month offered some concessions, including dropping the age for women from 63 to 60.
Communists beat candidates of the ruling party in elections to the regional parliaments of Khakasia, Irkutsk and Ulyanovsk regions.
Putin, who is 65, has attested that the pension age should be raised to 60 for women and 65 for men because there is an escalating burden on the pension system. Social media showed footage of police hitting protestors with batons in Moscow as their colleagues tried to wrench them out of the police's grip. While the Moscow and St Petersburg demonstrations were well covered by the worldwide media, two-thirds of the arrests were made in regional cities.
"I can't keep being afraid anymore", she said of her decision to risk detention by showing up at Moscow's Pushkin Square for the protest that attracted several thousand people.
The proposals have been heavily criticised by Russia's usually subservient press, with Moskovski Komsomolets, a popular Moscow newspaper, describing them as the "most unsafe and risky reform of President Putin's 20-year rule". He added that "hooligans and provocateurs" mixed up with protesters and assailed police.
Demonstrations also took place in Yuzhno-Sakhalinsk on a Pacific island and in Kaliningrad, the Russian exclave between Poland and Lithuania.
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He focused instead on the effort to support congressional candidates in amping up the crowd. He'll next travel to California for an event with seven House candidates in Orange County.
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The cascading effect that this hike has is considered strong enough to fuel an overall price hike and destabilise the economy. Unlike the previous governments, the BJP has also failed to cut excise duty whenever global oil prices shoot up.
"Putin and his government have plundered the budget for the past 18 years", Mr Navalny's team said in a pre-protest statement.
Anti-Kremlin protesters have rallied across Russian Federation in response to President Vladimir Putin's plans to hike the retirement age.
In Moscow, however, authorities have implemented an aggressive get-out-the-vote campaign, including promises of free concert tickets to voters and setting up polling stations outside of the city to enable voters spending the summer at their dachas to participate.
At least 2,000 people rallied in central Moscow, an AFP correspondent said, as the capital held a mayoral election the Kremlin-backed incumbent is sure to win.
Two independent liberal candidates were not allowed to run against him, while his four registered opponents are virtual unknowns.