Demonstrators shout slogans during an anti-corruption protest in central St. Petersburg, Russia, June 12, 2017. REUTERS/Anton Vaganov

MOSCOW (Reuters) - Police detained 500 protesters at an anti-Kremlin demonstration in Russia’s second-largest city St Petersburg on Monday, the Interior Ministry said.

Around 3,500 people participated in the unsanctioned protest, the ministry said in a statement.