The story behind Russia's elections
Police in Russia have made around 550 arrests after protests against Vladimir Putin's election as president, with protest leader Alexey Navalny among those held.
They detained 300 people in central St Petersburg out of a crowd of about 800 protesters, according to local police.
A further 250 were detained in the capital Moscow, including Mr Navalny, who was later released.
Foreign states have accepted Mr Putin won on Sunday but observers said the poll had been skewed in his favour.
Newsnight's Tim Whewell reports from Moscow, where he tracked down one of the buses protesters claim were used to ferry people between polling stations, to cast multiple votes in a practice known as "carousel" voting.