Police arrested a leader of Russia\'s liberal opposition on Saturday at the latest protest rally against fraud-tainted parliamentary polls. Officers picked up Sergei Mitrokhin, a leader of the Yabloko party at the end of the protest the party had organised, Yabloko spokesman Igor Yakovlev told AFP. Police said he had refused to obey official instructions, an offence for which he faced a possible fine or 15 days in jail, Yakovlev added. At the start of the protest, Mitrokhin had pushed back metal barriers placed there by police so more demonstrators could join them. Mitrokhin went on trial within hours of being taken to a police station, according to a posting on his Twitter account in which he added: \"My request to call witnesses has been denied.\" Police also arrested party activist Maya Zavialova, who organised the demonstration, because more protestors had attended than the number declared to the authorities beforehand, news agencies quoted a police official as saying. \"About 350 people took part in the event when authorisation had only been given for 300,\" a Yabloko spokesman said. \"After the demonstration, Zavyalova was taken to the police station for an administration infraction,\" the spokesman said, adding that she faced a possible fine. During the protest, participants set up two boards featuring pictures and names of election officials they claimed were involved in falsifications during the December 4 legislative vote. \"The country should know its anti-heroes,\" one activist said, an AFP correspondent reported. Others brandished party flags and chanted slogans calling for Vladimir Churov, the head of the Central Election Commission, to resign. This latest protest came amid continuing opposition to Prime Minister Vladimir Putin\'s plans to seek a third term as president. Opposition is growing more vocal to his 12-year rule, first as president, then prime minister. Yabloko founder Grigory Yavlinsky, who hopes to challenge Putin in March polls, released a statement calling for Mitrokin\'s immediate release, saying: \"The arrest of Mitrokin and the charges filed against him are excessive to the point of provocation.\" Lyudmila Alexeyeva, president of rights activists the Moscow Helsinki Group, said the arrest had been aimed at discouraging protests ahead of the March 4 presidential election. One placard depicted Churov in a light blue cloak and a wizard\'s peaked hat, an allusion to the popular nickname he earned after President Dmitry Medvedev called him a \"magician\" at a post-election meeting last month. Prime Minister Putin, who is seeking to return to the Kremlin in a job swap with Medvedev, is wrestling with the worst legitimacy crisis of his rule, with tens of thousands taking to the streets last month. A third major protest set for February 4 is expected to provide clues about the direction and strength of the nascent opposition movement. \"It is extremely important to turn up for protests, but mere protests are not enough,\" Mitrokhin said at the \"name them, shame them\" rally before his arrest, urging Russians to act as unofficial observers at the presidential election.