BBC – Russia’s main opposition leader, Alexei Navalny, has been arrested at an anti-corruption protest he organised in the capital, Moscow.
Thousands of people joined rallies nationwide, calling for the resignation of Prime Minister Dmitry Medvedev over corruption allegations.
At least 500 other protesters were detained in the capital and across the country.
Most of the marches were illegal, organised without official permission.
Hundreds of other protesters have been detained across the country, activists say.
TV pictures showed demonstrators chanting “Down with [Russian President Vladimir] Putin!”, “Russia without Putin!” and “Putin is a thief!”.
Correspondents say the marches appear to be the biggest since anti-government demonstrations in 2011/2012.