Russian police said they detained more than 260 activists in central Moscow on Sunday for holding an unauthorised protest against President Vladimir Putin.
The demonstration took place after radical opposition politician Vyacheslav Maltsev appealed on his website for supporters to hold protests across the country, calling for a "people's revolution" to end Putin's rule.
"For breaches of public order in central Moscow, 263 people have been detained. They have all been taken to local police stations," Moscow police said in a statement.
Many of those detained were carrying knives, knuckledusters and pistols that can fire rubber bullets, TASS state news agency reported.
An AFP photographer said police, some in helmets and bullet-proof vests, picked up the protesters one by one in central Moscow close to the Kremlin.
A reporter for popular Echo of Moscow radio station, Andrei Yezhov, wrote on Twitter that was detained, but he was later released without charge.
OVD-Info, a rights activist group that monitors political detentions, said that 286 people were detained in Moscow and 24 in six other cities.
The detentions come after police in Moscow on Saturday also detained dozens of people at an authorised nationalist anti-Kremlin march on a public holiday known as the Day of National Unity.
In recent months, opposition leader Alexei Navalny, who wants to stand against Putin in polls next year, has also called on his supporters to hold unauthorised protests, resulting in large numbers of arrests.
In June, more than 1,500 Navalny supporters were detained during a day of demonstrations across the nation. Thousands previously turned out in March for the biggest protests in years against the Kremlin, with police saying around 500 people were detained in Moscow.
Previously a little-known marginal figure, Maltsev ran for parliament last year as part of a coalition with former prime minister Mikhail Kasyanov despite opposition from some liberals who accused him of anti-Semitism.
The bearded 53-year-old activist calls himself a "Russian nationalist" and in a video released Saturday urged his supporters to "say no to Putin's regime".
Maltsev comes from the regional city of Saratov but fled to Paris earlier this year. A Moscow court later issued a warrant for his arrest over accusations of making public calls for extremist activity.
His movement, Artpodgotovka -- whose name refers to a military manoeuvre to deploy artillery -- was banned by a court in October.
The FSB security service said Friday that it had detained a group of Artpodgotovka members who were planning "high-profile extremist actions" on November 4 and 5 including setting fire to government offices and attacking police.
It said officers confiscated 15 Molotov cocktails during detentions in Moscow and the surrounding region.
The security service said police also shut down groups of his supporters in five other cities and accused Maltsev of using the internet for "propaganda of violent actions".
Maltsev told TV Dozhd (Rain) independent channel that the FSB had detained more than 100 of his supporters.
In a video statement last week, Navalny -- who is currently campaigning in Siberia -- accused the authorities of intimidating Maltsev and his supporters.
"People have a full right to gather, including on (November) the fifth," Navalny said. "What the authorities are doing against Artpodgotovka and specifically Maltsev is an absolutely illegal outrage."