The center of the Moscow protest is at Pushkin Square - and while NPR's Mary Louise Kelly says the crowd there is huge, she adds that it's also hard to ascertain how many people are there for Navalny's cause, and how many for the national holiday.
Navalny's decision to suddenly move the rally from its original to another location, thus make it unauthorized, was commented in different ways. In March, Navalny oversaw massive protests across Russian Federation, leading to his brief arrest, reportedly for disobeying a police officer.
A White House spokesman said the United States condemned the detentions.
Reporters witnessed hundreds of protesters being detained, with one non-government organization tracking the demonstrations reporting that at least 600 were arrested in the capital and another 300 in St. Petersburg.
More than 700 people were arrested in Moscow, while in St Petersburg, about 500 were forced into police buses at an unsanctioned rally that drew up to 10,000 people.
Those protests were the largest since a wave of anti-Kremlin demonstrations in 2012 and resulted in over 1,000 arrests, putting rare domestic pressure on Putin, who is expected to run for and win re-election next year. Similar crowds turned out March 26, rattling officials who had perceived the younger generation as largely apolitical.
Protesters in St. Petersburg toss a giant yellow duck meant to symbolize a corruption investigation of Prime Minister Dmitry Medvedev.
Tens of thousands of people still took to the streets, and more than 1,500 were arrested.
After the detentions, the protest appeared to be breaking up, but some demonstrators remained.
Trump lawyer: President not under investigation in Russia probe
Sekulow said his legal team had not received notice of any probe into Trump. "How do you know?" "You're right, Chris. The official demanded anonymity because the official was not authorized to be named discussing the deliberations.
Police detain a protester during a demonstration in downtown Moscow Monday. The police bundled him into a auto to prevent him from addressing a crowd of Moscow protesters. In response, Navalny had called on protesters to rally at an area in central Moscow which had been designated for public holiday celebrations.
The re-enactors watched the rally before riot police broke up the crowd and randomly seized the protesters.
On Monday, a wave of anti-government protests swept through multiple cities in Russian Federation, with people gathering in more than 200 cities to protest political corruption and stagnation.
As Vorivoda spoke, demonstrators chanted, "Putin is a thief!" and "Power to the millions, not the millionaires!"
A spokeswoman for Russian opposition leader Alexei Navalny says electricity has been cut at Navalny's offices in Moscow.
"This all looks like a very successful, well-constructed myth", he said of the protest campaign.
Nonetheless, Mr Nalvany's social media-savvy supporters have got their own YouTube channel - broadcasting from across the country.
Tverskaya, known in Soviet times as Gorky Street and one of Moscow's main thoroughfares, had been picked up by Navalny the location of a big protest rally on Monday.
Moscow police said Navalny would be charged with administrative offenses of resisting arrest and a second violation of demonstration organization rules. But Navalny switched it to Tverskaya Street, Moscow's main avenue near the Kremlin.
Navalny said contractors hired to build a stage at the agreed-upon venue couldn't do their work. His wife Yulia said plans for the protest would go ahead.
The current thorn in Putin's side is Alexei Navalny, blogger and opposition leader.
It warned that authorities would take all necessary measures to prevent provocations or any action threatening public security.