The unsanctioned protest was organized by Other Russia, a broad umbrella group that includes radical leftists, like National Bolshevik Party leader Eduard Limonov, as well as former chess champion Garry Kasparov and former Prime Minister Mikhail Kasyanov.
Protesters Accuse Putin
They accuse the Kremlin, under President Vladimir Putin, of stifling civil liberties ahead of the 2008 presidential election.
Demonstrators dubbed their rally the March of Dissent.
MORE: Coverage in Russian from RFE/RL's Russian Service.
Several hundred of them broke through a security cordon and marched along the city's main avenue before riot police armed with truncheons moved in, detaining scores of people.
RFE/RL Russian Service correspondent Tatyana Voltskaya, who covered the rally, said police actions to try to halt the event probably contributed to the violence.
“When I came I saw a very tight police cordon. The police had left only two very narrow corridors for people,” she said. “I would say that to be inside it was very unsafe because of a possible stampede."
“Police officers were speaking through megaphones," she said. "They urged people to leave the square and not to disturb the public order. It was not possible to hear what they were saying because the crowd was shouting ‘Disgrace, disgrace!’”
Protesters shouted "Russia without Putin!" and "Out with the corrupt authorities!" One group of protesters was dressed like clowns.
Police Beat, Detain Protesters
Voltskaya said violence broke out as thousands of people marched through the streets.
“The police were beating the protestors, pushing them away," she said. "They did not allow them to go as they planned to Suvorov Prospekt, so people turned to Nevsky Prospekt.”
Among those detained by police today was National Bolshevik leader Eduard Limonov.
Voltskaya says it was a disturbing experience to observe special police forces beating demonstrators, grabbing their flags and banners.
The demonstration comes ahead of local elections in St. Petersburg on March 11, elections to the national parliament this winter, and a presidential election on March 2 of next year in which Putin cannot take part, according to the current constitution.
(with material from agency reports)
Human rights activists Sergei Kovalyov (right) and Lyudmila Alekseyeva at the Other Russia conference in Moscow on July 11 (epa)
STATEMENT OF PRINCIPLES: Below is a translation of excerpts from the statement adopted by organizers of the Other Russia conference, which was held in Moscow on July 11-12. The conference brought together leading nongovernmental organizations and activists in an effort to show that Russian civil society continues to exist despite growing pressure from the Kremlin.
We are gathering because we are united by the most important thing -- our disagreement with the current course of the Kremlin and a growing alarm for the present and future of our motherland. We are gathering together, despite differences in our views about the past and the future of Russia. We are gathering together although we have differing conceptions of the paths our country must take toward freedom and development. Despite these differences, we are united by the following:
We, citizens of the Russian Federation, can achieve our stated goals only by observing, preserving, and demanding democratic principles of the organization of government and society; unshakeable human rights regardless of national, religious, or social status; respect for the views of others that do not contradict the Constitution of the Russian Federation; freedom of speech; honest political competition; and justice in the distribution of the national wealth, which is created by free people.
We oppose the transformation of Russia into a country ruled by bureaucratic whimsy; where the institutes of popular power and civil society are systematically destroyed; where the electoral process is completely controlled by the executive branch and, therefore, turned into a farce; and where the authorities demonstrate contempt for the interests of the majority of the population.
Lyudmila Alekseyeva, Moscow Helsinki Group; Viktor Anpilov, Working Russia; Mikhail Delyagin, Institute of Problems of Globalization; Yury Dzhibladze, Center for the Development of Democracy and Human Rights; Andrei Illarionov, Institute of Economic Analysis; Garry Kasparov, United Civic Front; Mikhail Kasyanov, Popular Democratic Union; Eduard Limonov, National Bolshevik Party; Yelena Lukyanova, lawer; Vladimir Ryzhkov, Republican Party; Georgy Satarov, INDEM foundation.