Hong Kong police used water cannon to fire blue-coloured water at protesters who defied a police ban and marched through the city.
The coloured liquid is traditionally used to make it easier for police to identify protesters.
Demonstrators lit fires, threw petrol bombs at riot police and attacked the parliament building.
The protest movement grew out of rallies against a controversial extradition bill – now suspended – which would have allowed criminal suspects to be sent to mainland China for trial.
Read more: Hong Kong anti-government protests