Police detained more than 50 people during a march in Moscow in memory of opposition leader Boris Nemtsov who was shot and killed near the Kremlin, a news report said.
The detainees were charged with violating public order during Sunday's mourning march, said the head of City Hall's security department, Alexei Mayorov, the Interfax news agency reported.
Among the detainees was Ukrainian lawmaker Oleksiy Honcharenko, who has since been released from custody and is sheltering in his country's embassy in Moscow, Ukraine's President Petro Poroshenko said Sunday on Facebook.
Honcharenko was scheduled to appear in court later Monday on charges of disobeying police orders, Interfax quoted his lawyer as saying.
Police said about 21,000 people took part in Sunday's march, while organizers put the number closer to 50,000.
The march was generally orderly and "stayed within the allocated time frame," Mayorov was cited as saying by Interfax.