Special police from Russia's Interior Ministry have reportedly detained several people, including opposition leader Ilya Yashin.
Opposition activists were gathering near the Barrikadnaya subway station in downtown Moscow after being evicted from a previous encampment in the Chistye Prudy area early on May 16.
Interfax quoted the Moscow police press service as saying when police were detaining two of the activists, others at the scene vandalized a police bus.
Police then detained "dozens" more, according to ITAR-TASS.
ITAR-TASS also reported there are some 1,500 opposition supporters now gathered in the Barrikadnaya station area.
Based on reporting by ITAR-TASS and Interfax