"The leader of the Russian Libertarian Party, Sergei Boyko, has been detained and taken to the Troitsk police department. He is charged with violating the article 20.2 [of the Administrative Code]", the spokeswoman said.
Earlier in the day, Ilya Azar, a journalist with Russia's Novaya Gazeta newspaper, and opposition activist Lyubov Sobol, who was detained on 2 September evening over an unauthorised rally held in Moscow last weekend, were released.
Unauthorised rallies have been held in Moscow since mid-summer after several pro-opposition candidates were excluded from the race to the Moscow parliament. Around 1,700 people were detained, with investigators opening criminal probes into staging unrest and using physical violence against law enforcers.
According to the city's authorities, the registration was denied due to the candidates’ failure to comply with the required procedures, while the opposition candidates view the denial as an infringement of electoral rights.
The election to the Moscow parliament is scheduled to take place on 8 September.