Ivan Golunov is known for his investigations into corruption among Moscow’s most powerful oligarchs.

A prominent investigative journalist has been arrested in Russia on drugs charges.

Ivan Golunov, known for his investigations into corruption in Russia, writes for online news source Meduza and has appeared on Al Jazeera.

He was arrested in central Moscow on Thursday while travelling to meet a source.

His employer said he managed to tell friends after his arrest that he was given two packages containing an unknown substance, which police later said were drugs.

Another bag reportedly containing drugs and scales was found in a police search of his apartment, Meduza said.

“We are convinced that Ivan Golunov is innocent,” Meduza’s Editors Galina Timchenko and Ivan Kolpakov said in a statement.

“Moreover, we have reason to believe that Golunov is being persecuted because of his journalistic activities.”

Peers described Golunov as one of Russia’s most dogged investigative reporters.

“This is totally incredible and is not in his character that he would give up what he’s been doing and start making money in this way,” Alexander Baunov of the Moscow Carnegie Center told The Associated Press. Baunov has known Golunov since 2004 when they worked together.

The oligarchs

Golunov, 36, faces being charged with the mass distribution of drugs, which carries a potential sentence of between 10 to 20 years in prison.

In 2014, the journalist secured one of the only interviews with fugitive Ukrainian oligarch Serhiy Kurchenko, who is wanted in Kiev on corruption charges and now lives under heavy security in Russia.

He appeared in Al Jazeera’s investigative documentary The Oligarchs, speaking about the interview and telling how Kurchenko’s aides offered him an envelope stuffed with cash, which they intended as a bribe for positive coverage.

Golunov said he left the money behind and wrote his article as he wanted.

Meduza said Golunov was recently threatened. Editors vowed to “protect our journalist by all available means.”

Dmitry Djulai, the journalist’s lawyer, told Reuters news agency he believed police planted the drugs on his client to frame him.

He said Golunov had been beaten and police refused to take swabs from his hands or rucksack or to take fingernail samples – all of which would have provided evidence of whether or not he had been in contact with drugs.

Djulai said police refused to call medics in order to catalogue and treat the injuries he said his client had suffered in custody.

International press freedom group Reporters Without Borders – known by its French acronym RSF – also suggested there were irregularities around Golunov’s detention.

“The extremely strange behaviour of the police suggests that Ivan Golunov has been arrested on a trumped-up charge,” Johann Bihr, the head of RSF’s Eastern Europe and Central Asia desk, told Al Jazeera.

“Why would they otherwise deny him access to his lawyer and refuse to carry out decisive tests? If fabricated evidence really has been used to arrest a journalist who is so well-known throughout Russia, this would mark a significant escalation in the harassment of the country’s independent media.”

The Russian investigator handling his case told Reuters he was not immediately able to comment.

In recent years a number of opposition figures and human rights activists have been arrested in Russia on what they say are phoney drug charges.

“This is widely seen as a tool the authorities use to persecute undesirables,” said Meduza.