Moscow police have released all but four of the more than 500 people who were detained during Wednesday's protest in support of freed journalist Ivan Golunov.
At least 549 people were detained in central Moscow at the protest, the OVD-Info police-monitoring website reported. The unauthorized march had originally been scheduled in support of Golunov, who was detained on drug charges late last week but was released on Tuesday over a lack of evidence.
Four protesters were held in administrative detention overnight, Interfax quoted the Moscow police press service as saying.
Several journalists and opposition figures were detained and later released on Wednesday, including protest organizers Yevgeny Berg, Ilya Azar and Elizaveta Nesterova and opposition leader Alexei Navalny.
More than 1,000 people attended the protest, organizers said.
Update: The protesters who had been held overnight have been released, OVD-Info reported Thursday.