The numbers were small in comparison with Sunday's mass demonstration, amounting to hundreds at some times and shrinking to a few dozen at others.
But by late Monday, police had made around 300 detentions, some the same people multiple times, according to RIA-Novosti, the state news agency. In contrast, 450 detentions took place Sunday, the agency said, citing police.
Monday's demonstrators faced an overwhelming police presence that refrained from the violence seen Sunday but seemed intent on keeping them far away from the Kremlin, where Vladimir Putin was sworn in for a third term as president.
Sunday's events — particularly who was to blame for the violent turn — was a frequent topic of conversation among protesters, many of whom blamed the police. Several protesters showed off battle scars from the day before, which they said they received at the hands of the police.
"I don't think people are going to arm themselves, but I think people don't see the point in carnival-like protests anymore and people want to force the regime to acknowledge them," said Masha Gessen, a co-organizer of Monday's flash mobs and editor-in-chief of Vokrug Sveta.
Others predicted a further escalation in the confrontation.
"I don't see any alternative to violence. We could rally peacefully for another 100 years and nothing would change," said Anastasia Gorodetskaya, 24, a lawyer's assistant.
Monday's flash mobs, which were leaderless and unsanctioned, again demonstrated protesters' lack of fear of the OMON riot police and increasing willingness to risk confrontation and detentions.
Police frequently forayed into the crowds to make detentions, the pretext for which was seldom clear, prompting protesters to complain that police were making arbitrary arrests.
Monday's gatherings were in sharp contrast to the earlier protests, which began in December against disputed State Duma elections and gathered tens of thousands of people who later peacefully dispersed.
Protestors first gathered at the start of Tverskaya Ulitsa by the Hotel National in response to calls to meet on Manezh Square, only to find access blocked. Riot police then pushed them up the street, detaining people one by one as they moved up past the Ritz Carlton hotel.
As they gathered, a man left the Ritz, entered a Mercedes with a blue light on top and left, presumably to go to the Kremlin inauguration down the road.
When police moved the protesters farther up the road, people attempted to line Gogolevsky Bulvar, where Putin's cortege was supposed to pass, in a rally of white ribbons, the symbol of the protest movement.
Police, however, blocked the boulevard, and the people moved up to Nikitsky Bulvar, where police raided the Jean-Jacques restaurant, a popular hangout for opposition figures and journalists, detaining people who were sitting outside.
Dozens of pro-Kremlin youth, many wearing cut-out hearts around their necks reading, "Putin loves everybody," approached people wearing white ribbons and attempted to hand out their own ribbons. At one point they gathered and chanted "Putin loves everyone" nonstop for 10 minutes.
Protesters clustered around the pro-Putin supporters, and scuffles broke out. When the pro-Putin supporters stuck a sign saying, "Putin loves everyone," around the neck of a small boy, his mother reacted angrily. "It's a sect," she said, without giving her name.
From there, the dance between the two sides moved to Tverskoi Bulvar, where hundreds of people headed toward Pushkin Square only to be chased back by riot police. Police vans lined both sides of the boulevard, and police officers were armed with fire extinguishers in response to flares and fires that tarnished protests Sunday.
The protesters' final destinations were Chistoprudny Bulvar — where police again picked off protesters, detaining people simply sitting on benches if they were wearing white ribbons, activists reported — and Staraya Ploshchad, close to the presidential administration office.
Police detained nearly everyone in sight — including, briefly, a Moscow Times journalist.
"We were walking down Chistiye Prudy, and two police vans raced up to a cafe," said Nadezhda Garanina, 35, an artist, who came from Chelyabinsk for the weekend's rallies. "People ran inside, and the OMON started dragging people out of the cafe. Five of them carried a woman out."
While protesters were rallying around the city's leafy tree-lined boulevards on Monday, dozens of detainees were seated in buses of all sizes, waiting for rulings outside a Moscow court. They were detained on Sunday near Bolotnaya Ploshchad and spent the night at police stations.
Daniil Tikhonov, a 30-year-old manager, traveled from St. Petersburg to Moscow especially to take part in the Sunday rally. He was arrested for the first time in his life along with the scores of other protesters.
"Usually, the police ignore me. Finally I was noticed!" Tikhonov told The Moscow Times outside the court, adding that he was "a disciplined person."
He said he had considered himself apolitical until the Duma elections in December. Tikhonov had stood in a chain of protesters swept by the riot police Sunday.
Finding himself in the police vehicle, he had been surprised to learn that there were no other managers among the 20 other detainees. Instead he was in the company of a taxi driver, a yard keeper, a factory worker, a theater director and a young man who described himself as a groom.
"I met people I'd never expected," Tikhonov said. He came to Moscow alone because none of his friends expressed interest in the protests. "I didn't really make a decision to go. … It was like in 'Matrix': I bought a ticket and came here."
Late Monday, he and his fellow detainees were driven back to a police station for the night. Their court hearing was scheduled for Tuesday. Opposition leaders Alexei Navalny and Sergei Udaltsov, meantime, triumphantly walked out of the building with minor fines for their participation in the protests Sunday.
Police guards at Tikhonov's minibus seemed as exhausted as the protesters after so many hours together and started accepting food provided to the protesters by supporters. The detainees said the guards had refused the food while at the station.
The group was delivered from the police station to the court by a shuttle mini-bus that normally travels from Moscow to suburban Balashikha.
"It's my off day today, but the boss called and said I should drive them," the mini-bus driver said, speaking on condition of anonymity because he was not authorized to comment. He said he doesn't know much about the opposition protests.
Navalny and dozens of others protestors were gathering just before midnight Monday near the Kitai Gorod metro station for what Navalny on Twitter called "an indefinite street party." In comments to those gathered that were recorded and posted on YouTube, Navalny told the people to call their friends to ask them to join the event and said there should be no alcohol and no tents because police would detain people who set up tents.
Staff writer Howard Amos contributed to this report.