After police started dispersing protesters in Mong Kok in the west of Kowloon, where an approved rally on Saturday, was suddenly transformed into a smoking battlefield in an unexpected turn of events, reports the South China Morning Post.
The organiser of the Mong Kok rally said about 120,000 demonstrators attended on Saturday.
The organisers' demands remained the same as at other rallies, that the government look into alleged abuse of police power; completely withdraw the now-suspended extradition bill; exonerate all protesters arrested; implement universal suffrage; and stop calling the protests a riot.
Later in the night, clashes flared in Wong Tai Sin after reports that the police had arrived to arrest two people. Hundreds blocked police vans from leaving, and attacked outnumbered officers with fire extinguishers, helmets, umbrellas and other objects.
Riot police used tear gas, pepper spray and batons in the streets of the densely packed neighbourhood, prompting many residents - some of them, such as elderly shirtless men, without protective gear - to join the protesters in turning on officers, accusing them of disrupting their community.
The stand-off in Wong Tai Sin lasted until around 4 a.m., with most of the protesters leaving after more rounds of tear gas were fired.
On Sunday, protests were planned in Tseung Kwan O and Hong Kong Island West, both densely populated residential districts.
Saturday's gathering comes after a group of civil servants - ordered to be politically neutral - joined demonstrations on Friday to address protesters' demands, the BBC reported.
Two months of demonstrations sparked by the controversial extradition bill have shown no signs of abating.
Mass protests began in March over the bill which would have allowed extraditions to mainland China.
Although the government has now suspended it, demonstrators want the bill fully withdrawn, and are widening their demands.
( With inputs from IANS )