The St. Petersburg authorities allowed the opposition to hold their March of Dissent rally April 15 but banned the demonstrators' plans to march afterwards. After the rally, most protesters went to a nearby metro station but some participants tried to break through a police cordon, which sparked clashes.
"About 150 persons participated in the clashes and about 120 of them were detained," the spokesman said.
According to data of the city's interior department, a total of about 500 people participated in the opposition rally in St. Petersburg.
The rally followed a similar opposition protest in Moscow April 14 where about 250 protesters were detained.
Human rights advocates in Russia and abroad have criticized the Kremlin for tightening its grip on democracy and human freedoms ever since Vladimir Putin took presidential office in 2000. However, polls show that the majority of Russians support the country's leader for stability and economic growth Russia has enjoyed under his rule.