Russian police detained more than 30 activists on Saturday who marked Constitution Day with protests in Moscow over alleged human rights abuses.
Explaining the circumstances of his arrest from a police station in central Moscow, Sergei Mitrokhin, head of the Yabloko liberal party, told the AFP news agency: "I was holding a placard that read 'Respect our Constitution.'"
He said he was manhandled and detained by three police officers, who had told him his "safety was under threat" because workers were putting up a Christmas Tree in the central square where the activists staged individual protests.
Mitrokhin said he was accused of resisting police and would likely face 15 days in jail. He was last detained about a month ago, he added. Several other activists were also detained.
Mitrokhin and others had attempted to circumvent a rally ban imposed by the authorities by each staging their own one-person protest.
Activists do not need formal permission from the authorities for single-person demonstrations.
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More activists were detained when they turned up in the city centre for another unauthorised rally after the authorities said the opposition was not allowed to hold a march, citing preparations for the New Year's holidays.
Activists tracking arrests at opposition protests said 33 people had been detained, including rights activist Lev Ponomaryov and Georgy Satarov, a former aid to Russia's first president Boris Yeltsin and one of the authors of the country's constitution.
There was no immediate comment from police.
Under recent changes to Russia's law on rallies, anyone found to have violated the legislation three times within six months faces up to five years in prison.
The latest arrests came after a court earlier this week sentenced a young activist, Ildar Dadin, to three years in jail for repeatedly staging solo protests criticising Russian authorities, the first activist to be handed down such a tough sentence under the new law.
Amnesty International called his jailing "a shocking and cynical attack on freedom of expression".
Activists have complained that since the seizure of Crimea from Ukraine last year, Russian authorities have clamped down on peaceful protests, leaving critics with few outlets to express their disagreement with Kremlin policies.