Several thousand opposition supporters have gathered in central Moscow for an unauthorised rally and at least one prominent opposition figure has been detained.
Opposition leaders had applied for permission to hold a march marking a year since a wave of massive protests against Vladimir Putin and the government arose, but city authorities refused to allow the gathering.
There was a heavy police presence around the approximately 3,000 activists who came to Lubyanka Square for the rally. The square is outside the headquarters of the Federal Security Service, the main successor agency of the Soviet KGB.
Russian riot police detained at least three opposition leaders as they tried to attend the rally, witnesses said.
Leftist leader Sergei Udaltsov raised a fist in the air as police grabbed him under the arms and hauled him away into a waiting van near Lubyanka Square.
Ilya Yashin said on Twitter that he and Ksenia Sobchak, both of them prominent members of the opposition, were detained as they made their way to the rally in front of the former KGB security police's headquarters on Lubyanka Square.
The rally is intended to mark 12 months of protests against Mr Putin that have included the biggest demonstrations against the former KGB spy since he rose to power 13 years ago but failed to prevent him winning a six-year third term as president in March.
Moscow city authorities refused to give the opposition permission to hold the protest and police told people to leave as they gathered on Lubyanka Square despite freezing cold.