Russian riot police detained at least three opposition leaders on Saturday as they tried to attend a banned rally against President Vladimir Putin, 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 in central Moscow, where several hundred people had gathered for the rally. 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 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.