Alexei Navalny, Russia’s main opposition has been arrested in the capital, Moscow.
Navalny had just arrived to join in an anti-corruption rally he organised, calling for the resignation of Prime Minister, Dmitry Medvedev.
Thousands of people were at the protest, which also took place nationwide. Hundreds of people were detained by the police.
In a tweet after his detention, he urged fellow protesters to continue with the demonstration.
He later said police stormed the office of his foundation and detained its staff, who were broadcasting the protests live.
He had called for the protests, after he published reports claiming that Mr Medvedec controlled mansions, yachts and vineyards, a fortune that far outstripped his official salary.
