- "Cops are laughing at what they are doing," Pivovarov said.
MOSCOW: Russian police on Saturday arrested around 200 opposition politicians and municipal deputies at a Moscow conference as authorities tighten the screws on Kremlin critics ahead of parliamentary elections.
A police raid on an opposition conference dedicated to running for municipal office came after President Vladimir Putin's top critic Alexei Navalny was jailed for two and a half years last month and more than 10,000 protesters detained across the country.
While Russian police routinely break up opposition protests, the mass arrests of municipal deputies at a conference in Moscow were unprecedented.
Participants from more than 50 of Russia's regions had gathered to discuss parliamentary and local elections in September at a forum organised by a project backed by prominent Kremlin critic Mikhail Khodorkovsky.
Forty minutes into the conference police broke up the event and detained the participants.
"The ENTIRE forum of Russian municipal deputies has been detained in Moscow!" Khodorkovsky said on Twitter, calling the detentions "unconstitutional".
As news of the detentions emerged, US Secretary of State Antony Blinken called for an end to "persecution of independent voices", noting the Kremlin had detained these people "on dubious grounds".
A number of well-known opposition figures including Ilya Yashin, Vladimir Kara-Murza, Yulia Galyamina, Yevgeny Roizman and Andrei Pivovarov as well as journalists have been detained.
"A very symbolic end to a short forum: deputies in police vans, and masked police are twisting people's arms," Yashin said on Facebook.
Moscow police said in a statement that around 200 people had been detained.
Many of the conference participants did not wear masks, while some were members of an organisation whose work had been declared "undesirable," police said.
Pivovarov, speaking to AFP from a police station, said the forum participants had been detained because authorities believe the conference was organised by Open Russia, a movement founded by Khodorkovsky and designated as an "undesirable organisation".
The municipal forum -- the first of its kind -- was organised by United Democrats, another project backed by Khodorkovsky, Pivovarov said. The authorities had appeared to look for a pretext to interrupt an opposition event, he said.
A number of the detained activists said Saturday evening they had been released but ordered to appear in court at a later stage.
Taking to Twitter Saturday night, Pivovarov said police admitted to him that they had been under pressure to clamp down on the Kremlin critics.
"Cops are laughing at what they are doing," Pivovarov said.
Khodorkovsky's Open Russia was banned in Russia in 2017 in line with a controversial law targeting foreign groups accused of political meddling.
People cooperating with "undesirable" entities could be hit with fines and Russian entry bans.
Khodorkovsky, who owned the oil giant Yukos before he was convicted in two controversial cases and spent a decade behind bars, now lives abroad.