The suburb of St Louis has been inflamed with racial tensions since Aug 9 when a white policeman, Darren Wilson, shot dead a black teenager, Michael Brown, 18, Xinhua reported.
Before the shooting, Wilson had tried to stop Brown for walking in the street, disrupting traffic.
Police fired at least 75 rounds of tear gas at a crowd of more than 5,000 protestors as they marched toward a police command post Sunday night.
The protestors, who retreated shortly after 9.00 p.m., hurled Molotov cocktails towards police officers before the latter's firing of tear gas, St. Louis county police said.
Seven arrests were made on Saturday night as police used smoke bombs and tear gas to disperse a crowd of about 150 in Ferguson, after being called to the scene of a disturbance at a restaurant after the curfew started.
The US justice department is investigating the shooting of Brown, with 40 Federal Bureau of Investigation (FBI) agents dispatched to Ferguson to gather information.