Police in Moscow arrested around 20 government opponents holding a peaceful protest against the jailing of former vice premier Boris Nemtsov, Interfax news agency reported Monday.
Nemtsov, a leading critic of the Kremlin, was sentenced to 15 days detention on Sunday for resisting arrest during an unauthorized demonstration on New Year's Eve.
The verdict has aroused widespread anger among human rights activists and members of Russia's non-parliamentary opposition. Civil rights activist Lev Ponomaryov accused Prime Minister Vladimir Putin's government of launching an assault on elements of society who disagreed with it.
The treatment of ex-oligarch Mikhail Khodorkovsy, jailed last week for stealing oil from his now defunct company, Yukos, was intended to apply pressure on civil society, he said. Nemtsov was the third prominent government opponent to be jailed in fast-track trials since police forcibly broke up the December 31 demonstrations, arresting around 120 people.