Russian mayor and opposition figure, Yevgeny Urlashov, was detained Tuesday night on corruption charges.
Urlashov's election last year as mayor of Yaroslavl was a blow to Russian President Vladimir Putin and his party United Russia.
The mayor left Putin's United Russia in 2011, joining the Civil Platform party led by liberal billionaire Mikhail Prokhorov. He is one of few anti-Putin officials to hold public office in Russia.
He won the mayorship of the town, 150 miles from Moscow, on an anti-corruption ticket in April with 70 percent of the vote.
Urlashov was set to lead a list of candidates for Civil Platform in September's regional elections.
He was stopped at a roadblock by police late last night and was detained. He was later accused of extorting a 14 million Russian roubles ($420,000) from a firm that repaired and cleaned the streets in Yaroslavl.
The mayor faces up to 15 years in jail if convicted.
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Civil platform and critics of Putin believe that the arrests of opposition figures are meant to silence dissent.
"It is obvious that this night-time show ... had a single aim: to scare Yevgeny and all other independent politicians and active citizens of Russia," Mikhail Prokhorov, leader of the independent Civil Platform party, said in a statement.
Opposition members believe that Putin is using the judiciary for political ends - a charge he denies.
Civil Platform helped organize some of the largest anti-Putin protests after his third presidential election win in March 2012.