The riots were caused by the anti-cholera measures, undertaken by the tsarist government, such as quarantine, armed cordons and migratory restrictions. Influenced by rumors of deliberate contamination of ordinary people by government officials and doctors, agitated mobs started raiding police departments and state hospitals, killing hated functionaries, officers, landowners and gentry. In November 1830, the citizens of Tambov attacked their governor, but they were soon suppressed by the regular army. In June 1831, there was a riot on the Sennaya Square in St.Petersburg, but the agitated workers, artisans and house-serfs were dispersed by the army, reinforced with artillery. The riots went especially out of control in Sevastopol and in military settlements of the Novgorod guberniya. The rebels established their own court, electoral committees out of soldiers and non-commissioned officers and conducted propaganda among the serfs.