The mass arrests at the unauthorized rally provided a harsh coda to the elation of journalists and other supporters of Ivan Golunov a day after Russia's interior minister announced the unprecedented move to drop the charges and seek punishment for the police officers involved.
"We should not stand down, even if Ivan is free. There are a number of other people in his situation in this country," said Maxim Reznik, a member of the St. Petersburg City Council who attended a smaller demonstration in that city.
Police said more than 200 were detained in the Moscow demonstration, but the OVD-Info organization that monitors political arrests put the figure at more than 400.
The Interior Ministry said about 1,200 people took part in the Moscow demonstration, and those arrested faced charges that could bring up to 20 days in jail, state news agency Tass reported. Among them was Alexei Navalny, President Vladimir Putin's most prominent foe.
Golunov, a reporter for the website Meduza, was arrested June 6 for allegedly dealing synthetic stimulants. Many believed he was set up as retaliation for his reporting on Moscow City Hall and the city's crime-ridden funeral industry.
Information quickly surfaced indicating Moscow police acted based on falsified evidence and sham allegations.
In announcing Golunov's arrest, police posted photos of drugs allegedly taken in the journalist's apartment, but then admitted the images came from another case. Defense lawyers said his fingerprints weren't on any of the drug packets allegedly found in his apartment.
An outcry over his arrest intensified quickly, apparently catching authorities by surprise. Objections to Golunov's treatment were reported in unusual detail by Russian state media that generally hew closely to official versions.
Three of Russia's most respected newspapers published near-identical front pages Monday reading "I/we am/are Ivan Golunov." Even the powerful speaker of Russia's upper house of parliament expressed concern about the case.
Russian human rights activists have often complained to little effect of fabricated criminal cases against opposition figures and those who raise inconvenient questions about sometimes-shady businesses.
While the unusual prominence of Golunov's case could be seen as a watershed in drawing attention to the issue, observers also said it was only the beginning of a long struggle to hold authorities accountable.
"The case against Golunov is actually over. But the case against the system in which such lawlessness became possible is just beginning," Maria Zheleznova, opinion editor of the newspaper Vedomosti, wrote in a piece published Wednesday.
However, the police action at the Moscow demonstration showed that authorities intend to keep tight control over public protest. Opposition groups are routinely denied permission to hold rallies or sometimes given permission for gatherings at undesirable times or low-visibility locations.
Authorities had said the pro-Golunov demonstrators could hold a rally on Sunday, but protesters believed a delay could have sapped a sense of momentum.