Russian police arrested more than 100 demonstrators protesting constitutional reforms that could keep Vladimir Putin in power for 16 more years, a human rights monitoring group said.
About 500 people, many wearing face masks branded with the word "no," marched down a major street Wednesday in the Russian capital.
Some waved banners demanding that Putin resign, while others called the Russian president a "thief."
OVD-Info, an independent political monitoring group, reported more than 100 arrests, but police and Russian officials made no comments.
"I came here to sign the petition against the constitutional reforms because I am a nationalist," one protester told Reuters, while a teenage girl blamed Putin for "the poverty in our country."
Russian voters this month approved changes to the constitution that allow Putin to remain president until 2036. Without the amendment, he would have been required to step down in four years.
The opposition said the vote to amend the constitution was rigged.
Putin has been in control in Russia as president or prime minister for 20 years.