Hong Kong police made around 30 arrests, as the pro-democracy rally on Saturday descended into violence.
Reports say police used pepper spray and tear gas to break up the crowds, after a number of activists threw bricks and Molotov cocktails.
Others attacked recently-installed smart lamp posts. which have been suspected by some as a state surveillance tool.
The protests started in June over a now-suspended extradition bill that would allow Hong Kong locals to be sent to China.
The movement has now widened to demand free elections and an independent probe into alleged police brutality and collusion with gangs to suppress the rallies.