Alexei Navalny, 36
Corruption-fighting lawyer and popular blogger has played a role in mobilising Russia's youth to rally against Vladimir Putin's rule. Spearheaded series of rallies in Moscow during the winter that brought up to 100,000 people in the streets.
Sergei Udaltsov, 35
Leader of the Left Front opposition movement, he has been at the forefront of anti-Putin protests for several years. Great-grandson of a Bolshevik revolutionary, he has consistently defied authorities, staging unsanctioned marches and rallies.
Ksenia Sobchak, 30
Socialite, TV host and restaurateur, she has become a new glamorous face of the opposition (pictured at left). Daughter of late mayor of St Petersburg who was Mr Putin's mentor in the 1990s. Personal relationship with Mr Putin initially seemed to shield her from reprisals, but that seems to have come to an end with Monday's raid on her apartment. Tweeted that investigator told her she made a mistake by mixing with "bad company."
Ilya Yashin, 28
Member of the leadership of the opposition Solidarity movement, has been among key organisers of recent anti-Putin protests. A fiery speaker and a fierce critic of the government. Wrote on his blog: "A smart government deals with reasons for protest. A stupid government fights protesters."