Hundreds of protesters have been arrested at a demonstration in Moscow sparked by the detention of a top investigative reporter last week.

Ivan Golunov was freed on Tuesday following an unprecedented show of media and popular solidarity. All charges against him were dropped and senior police officers were reportedly fired over the alleged planting of narcotics on his person.

Despite the journalist’s release, his supporters on Wednesday decided to go ahead with the unsanctioned demonstration in Russia‘s capital to demand punishment for those involved in his alleged framing.

Among those arrested at the rally was opposition leader Alexei Navalny, a prominent political rival of President Vladimir Putin.

“Police ordered people to leave the unauthorised protest, but the protesters were defiant,” Al Jazeera’s Step Vaessen, reporting from Moscow, said.

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“They protested not only against the arrest of Golunov, but to show their anger at the oppression against the media, and to protest against the system – that people can be arrested on these fake charges here in Russia.”

Police said more than 200 protesters had been arrested, though OVD Info, a group monitoring arrests of opposition figures, put the figure at at least 400.

The interior ministry said about 1,200 people took part in the demonstration and that those arrested would face charges that could bring up to 20 days in jail, state news agency Tass reported.

Golunov, a 36-year-old reporter for the Meduza website, was arrested last week for allegedly dealing synthetic stimulants. His lawyer said he was beaten in custody and information indicating the charges were falsified quickly surfaced.

Police posted photos of drugs allegedly taken in his apartment, but later admitted they were from another case. State TV reported that Golunov had been intoxicated when arrested, but retracted the claim after it was pointed out that a medical document shown in the report specified that he wasn’t. Lawyers said his fingerprints weren’t found on any of the drug packets allegedly found in his apartment.

On Monday, three leading Russian newspapers – Vedomosti, Kommersant and RBC – each published front-page headlines reading: “I am/We are Ivan Golunov,” accompanied by editorials calling for inquiries into the case.

“We do not rule out that Golunov’s detention and subsequent arrest are linked to his professional activities,” they said, adding that the journalist’s detention amounted to an act of intimidation.

Golunov has built a career out of investigating corruption and criminality among Russia’s most powerful oligarchs, and many in the Russian capital believe he was set up as retaliation for his reporting on Moscow City Hall and the city’s crime-ridden funeral industry, The Associated Press news agency reported.

He featured in a 2018 Al Jazeera investigative documentary, The Oligarchs, in which he told the story of securing a rare interview with fugitive Ukrainian Serhiy Kurchenko, only to be met at gunpoint with an attempted bribe.

Russian human rights activists have often complained – to little effect – of fabricated criminal cases against opposition figures and people inconvenient to questionable businesses. While the unusual prominence of Golunov’s case could be seen as a watershed moments in efforts to draw attention to the issue, observers also said it was only the beginning of a long struggle.

“The case against Golunov is actually over,” wrote Maria Zheleznova, opinion editor of Vedomosti, one of the three papers that showed front-page support for Golunov. “But the case against the system in which such lawlessness became possible is just beginning, otherwise such cases will necessarily arise again and again.”