Police in Russia have made 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.
A further 250 were detained in the capital Moscow, including Navalny, who was later released.
Foreign states have accepted Putin won on Sunday but observers said the poll had been skewed in his favour.
UK Prime Minister David Cameron phoned Putin to say he was looking forward to working with him to "overcome the obstacles in the relationship between Britain and Russia and build deeper political and trade links.