It is a rare U-turn by authorities in the face of anger from Golunov's supporters, who alleged he was framed for his reporting and who threatened to stage a mass protest in Moscow.

Golunov, a 36-year-old journalist known for exposing corruption among Moscow city officials, was detained by police on Thursday last week and accused of serious drug offences, which he flatly denied.

Russian journalists critical of authorities have led a dangerous existence since the 1990s - sometimes threatened, physically attacked, and even murdered for their work.

But the crude way supporters said Golunov was set up and detained triggered an unusual show of media unity and an uncharacteristically swift response from authorities nervous about social unrest at a time when President Vladimir Putin already faces disquiet over living standards.

Interior Minister Vladimir Kolokoltsev said in a statement on Tuesday that the criminal case against Golunov was being dropped due to a lack of evidence of any wrongdoing on his part.

He said the journalist would be freed from house arrest later on Tuesday.

Some police officers involved in the case were being temporarily removed from duty pending an investigation, he said, adding that he planned to ask Putin to dismiss other more senior police personnel.

"I believe that the rights of every citizen, regardless of his profession, must be protected," Kolokoltsev said.

The climb-down prompted joy from Golunov's supporters, including Galina Timchenko, general director of online news portal Meduza where Golunov works.

"I am happy, I'm crying. We understand perfectly that this happened thanks to the efforts of hundreds and thousands of people. Huge gratitude to all of them," he told the Interfax news agency.

Australian Associated Press