MOSCOW - A Russian opposition politician whose victory in a mayoral election embarrassed President Vladimir Putin was detained on Wednesday in a corruption investigation which allies said was intended to silence dissent.

A spokeswoman for Yevgeny Urlashov, mayor of the city of Yaroslavl, said police dragged him out of his car when he stopped at a road block during the night and the Interior Ministry confirmed his detention.

Federal investigators said Urlashov, his deputy and two other officials were suspected of demanding a 14-million rouble ($425,000) bribe from the head of a company that has street cleaning and repair contracts in the city 250 km (150 miles) northeast of Moscow.

Russian news agencies said police had searched their homes and the mayor's office.

"It is obvious that this nighttime show ... had a single aim: to scare Yevgeny and all other independent politicians and active citizens of Russia," said billionaire Mikhail Prokhorov, leader of the independent Civil Platform party. Urlashov is a member of the party's governing committee.

Urlashov defected from the ruling United Russia party in 2011 to join a protest movement that mounted the biggest opposition rallies of Putin's 13 years in power. Urlashov's landslide election victory in Yaroslavl in April 2012, as an independent, underscored discontent with Putin's ruling elite.

Putin's critics accuse him of cracking down on the opposition since his return to the Kremlin in May 2012 and several opposition leaders have faced criminal charges, although the Kremlin denies using the judiciary for political ends.

Urlashov's spokeswoman, Svetlana Yefimova, was quoted as saying on the Civil Platform website that police had "pulled him out by the scruff of the neck and drove him away without explaining the reason" after stopping his car after midnight.

($1 = 33.0615 Russian roubles)