ST. PETERSBURG, Russia – Police clubbed protesters and dragged them into waiting buses on Saturday in response to a defiant demonstration against the Kremlin in the heart of President Vladimir Putin’s hometown. Several thousand members of liberal and leftist groups chanted “Shame!” as they marched down St. Petersburg’s main avenue to protest what they said was Russia’s rollback from democracy. The demonstration, called the March of Those Who Disagree, was a rare gathering of the country’s often fractious opposition. It was at least the third time police have moved in to break up an anti-Kremlin protest in recent months. St. Petersburg authorities had prohibited the march, only granting permission for a rally far from the city center, but the activists defied the ban and marched down the Nevsky Prospekt, the city’s main street, blocking traffic. The mayor called the protesters extremists trying to destabilize the city ahead of local elections. Russia’s state-controlled television stations covered the protest only briefly, portraying the demonstrators as hooligans and extremists. The sidelined and often divided opposition has faced increased harassment in recent years, with protest meetings barred on suspicious legal grounds or party congresses broken up or canceled for no reason. Putin’s policies have drawn criticism from the United States, straining ties between the two countries. In December, police pulled hundreds of opposition activists off buses and trains and detained them ahead of an anti-government demonstration in Moscow. The next month, police arrested dozens of Bolshevik party members rallying in support of activists detained in earlier unauthorized protests. 160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set! Riot police beat dozens of protesters with truncheons, but several thousand broke through police cordons. They marched toward the city center and rallied for about 40 minutes until police moved in again, detaining people and dragging them into buses. Several activists attacked a law enforcement officer. Between 20 and 30 people were detained, the ITAR-Tass reported, citing police officials. Garry Kasparov, former world chess champion who helped organize the event, said on Ekho Moskvy radio that the participants numbered up to 6,000, though the crowd appeared to be about half that number. Among those detained were the head of the radical National Bolshevik Party and an independent city legislator. “The authorities are destroying … the constitutional structure, rights and freedoms,” former Primer Minister Mikhail Kasyanov, who now heads on opposition movement, told AP Television News. “Unfortunately we are going through a very difficult time in our country, but we will continue to fight for our rights.” The activists accused Putin’s government of cracking down on the opposition, stifling freedom of speech and eating away at democratic institutions by abolishing direct elections of provincial governors and creating an obedient parliament.