MOSCOW -- Russian riot police officers have detained opposition leader Alexei Navalny during an unauthorized rally in Moscow to protest against President Vladimir Putin, two days ahead of his inauguration for a fourth Kremlin term.
Navalny's arrest on May 5 came as hundreds of his supporters were also detained by police at anti-Putin rallies across Russia.
Putin is due to be sworn in for his fourth term as Russia's president on May 7, extending an 18-year reign that his supporters say has lifted the country "from its knees" and is denounced by his opponents as a corrupt, calcifying autocracy.
Navalny, who has organized large street protests and published a series of reports alleging corruption in Russia's ruling elite, was barred from the presidential ballot in March due to a conviction on financial-crimes charges he contends were fabricated.
He had called for nationwide anti-Putin protests ahead of his fourth presidential inauguration under the slogan "He's not our tsar."
Rallies were due to take place in up to 90 cities and towns on May 5, including Moscow and St. Petersburg, although few received authorization from local officials.
Authorities in Moscow had warned Navalny supporters about taking part in the planned protest in the Russian capital, calling it "absolutely unlawful."
In Moscow, riot police detained some protesters, while men, in traditional Cossack dress, were seen beating some of the demonstrators as a police helicopter flew above the crowd.
Among the crowd on Pushkin Square were pockets of pro-Putin supporters, many of them young men.
Pro-Putin activists shouted "Our country, our rules" and "We are for Putin."
In the Siberian city of Krasnoyarsk, the Siberia Desk of RFE/RL's Russian Service says 150 people were detained following clashes between protesters and baton-wielding police.
In Yakutsk, 75 protesters were detained by police at the rally there, according to a Navalny supporter.
In Novokuznetsk, police detained some 20 protesterstaking part in the rally there.
In Khabarovsk, protesters chanted "Down with the tsar" at the rally in that Siberian city.
On the eve of the protest action, Navalny supporters were detained by police in several Russian cities including St. Petersburg, Krasnoyarsk, Krasnodar, Tambov, Kemerovo, and Cheboksary.
In the Urals city of Yekaterinburg, meanwhile, police searched Navalny’s regional headquarters and confiscated leaflets advertising the May 5 rally.
A coordinator for Navalny the southern city of Volgograd, Aleksei Volkov, wrote on Twitter that students at local schools were forced to sign papers acknowledging that they could face serious consequences, including expulsion, if they take part in the rally.