Police in Hong Kong fired water cannons and tear gas at protesters in the city on Sunday.
Some demonstrators dug up bricks from the pavement and at least one petrol bomb was thrown.
The Chinese-ruled city's MTR rail operator suspended some services to try to prevent people gathering but protesters made it to a sports stadium in the vast container port of Kwai Chung, from where they marched to nearby Tsuen Wan.
The brief clashes followed another day of violence on Saturday when the authorities used tear gas for the first time in over a week.
Protests have been going on for three months — they started as a response to proposed new legislation on extradition but have grown into a fight against what many see as the erosion of the "one country, two systems" arrangement under which Hong Kong was returned to China by the British in 1997.
This is the biggest challenge to Chinese rule since that handover.
More than 700 people have been arrested since the start of the protests.
Beijing has warned that more forceful intervention is a possibility and paramilitary forces have been holding drills nearby.