Around three thousand demonstrators blocked a major road in the city's congested Mongkok district in Kowloon, bringing traffic to a standstill and opening up a second significant flash point in the key financial hub.
A dozen police looked on helplessly as the demonstrators took over Nathan Road, chanting slogans and wrapping their eyes in cling film to protect themselves in the event of pepper spray being deployed, an AFP reporter said.
Some of those demonstrating in Mongkok said they took their protest across the harbour because it was safer there.
"We need to strike for freedom and for our democracy. We've come to Mongkok because it's very dangerous now in Central and Admiralty," 20-year-old student Calvin Chan told AFP, referring to the two districts where tear gas had been deployed.
Pro-democracy groups are locked in a struggle with the city's authorities over China's refusal to grant unfettered democracy.