Police officers detain opposition leader Alexei Navalny during an unauthorized rally in Lubyanka Square in Moscow, Saturday. Thousands of opposition supporters have gathered in central Moscow for an unauthorized rally where several prominent opposition figures have been detained. — AP MOSCOW — Russian riot police detained four opposition leaders on Saturday to stop them taking part in a banned rally against President Vladimir Putin in front of the former KGB security police's headquarters in Moscow. The rally was intended to celebrate the first anniversary of demonstrations that grew into the biggest protests against Putin since he rose to power 13 years ago, but police were out in force to keep order and helicopters buzzed overhead. Despite the risk of arrest, protesters stood clapping. Some chanted “Free political prisoners” and “Down with the police state.” One unfurled a banner saying “crooks and thieves” - the popular name used to describe the Russian leadership. Leftist Sergei Udaltsov and anti-corruption blogger Alexei Navalny were detained on the central Lubyanka Square, where witnesses said about 2,000 people gathered, and protest leaders Ilya Yashin and Ksenia Sobchak were detained on their way. “The bloody regime has got to Sobchak,” Navalny said before he was hauled away, referring to the 31-year-old former socialite who has joined the opposition even though her late father was once St Petersburg mayor and a close ally of Putin. Moscow city authorities refused to authorise the protest and police in helmets and flak jackets told people to leave as they gathered for the rally despite the freezing cold. “I don't know how many people are here but I am proud of each and every one of those who came here. The main thing is that people are here, that they are expressing their view and showing that they exist,” Navalny told reporters. — Reuters