Some 2,000 anti-Kremlin protesters joined May Day rallies in Saint Petersburg, chanting slogans critical of President Vladimir Putin, as police arrested more than 30 people.
Protesters included supporters of top opposition leader Alexei Navalny while several thousand members of the ruling party, Communists and other activists also turned out in the centre of Russia's second city.
Anti-Kremlin marchers held up portraits of the Russian strongman, chanting "Putin is a thief!" and "This is our city" amid a tightened police presence.
"They are protecting Putin the bandit," said 70-year-old Galina Onishchenko, pointing to prisoner transport vehicles.
Among those detained were several who chanted anti-Putin slogans.
Activists yelled "fascists" and "you will not scare us", an AFP reporter said.
More than 30 people were detained in the city, said OVD-Info which tracks opposition arrests.
Thousands of Communists also demonstrated in the capital Moscow and across the country, waving red flags, in celebrations harking back to the Soviet-era.
Popular discontent has been building in Russia over the past few years amid controversial pension reforms and falling living standards following numerous rounds of Western sanctions over Ukraine and other crises.
The Russian president's popularity ratings have taken a beating and in March he signed off a law that allows courts to fine and briefly jail people for showing disrespect to the authorities.
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