Russian riot police have dispersed thousands of opposition protesters from the main square in St. Petersburg, detaining at least 20 people. More than 2,000 demonstrators turned out for Saturday's banned "March of Dissent," which was organized by the opposition umbrella group, Other Russia. Demonstrators carrying banners and shouting anti-government slogans broke through a police cordon in central St. Petersburg to marched down the main avenue. They interrupted the traffic flow until police forced them away. The government refused to give permission for the march, which comes ahead of local elections. It suggested a rally be held outside the city center instead.