The protesters, most of them young people dressed in black, erected barricades as they prepared for an extended occupation of the area, in scenes reminiscent of pro-democracy Occupy rallies that rocked the city in 2014. Protesters massed in and around Lung Wo Road, a main east-west artery near the offices of embattled Hong Kong Chief Executive Carrie Lam. Hundreds of riot police, some armed with batons and plastic shields, warned them to stop advancing.
One eyewitness said rubber bullets and CS gas were fired by police at protesters.
Galileo Cheng said on Twitter: “Essentially police are shooting anyone getting close, including journalists.”
He also tweeted two videos of police lined up and appearing to show officers firing at people.
But one young protestor wearing a black mask and gloves said: “We won’t leave till they scrap the law.
“Carrie Lam has underestimated us. We won’t let her get away with this.”
Many of the protesters, who skipped work, school or university to join the rally, defied police calls to retreat and passed around provisions, including medical supplies, goggles, water and food.
Some stockpiled bricks broken away from pavements.
Pro-democracy campaigner Claudia Mo said: “Didn’t we say at the end of the Umbrella movement we would be back? Now we are back!”
Opposition to the bill on Sunday triggered Hong Kong’s biggest political demonstration since its handover from British to Chinese rule in 1997 under a deal guaranteeing it special autonomy.
The government said the debate on the bill due to take place today in the 70-seat Legislative Council would be delayed until further notice. The legislature is controlled by a pro-Beijing majority.
Hong Kong Chief Secretary Matthew Cheung urged the protesters to stop occupying the road and appealed for calm and restraint.
He said: “We also appeal to the people who are stationed to disperse as soon as possible, and not to try to defy or challenge the law.”
Ms Lam has sought to soothe public concerns and insisted her administration was creating additional amendments to the bill, including safeguarding human rights.
Under the proposed law, Hong Kong residents, as well as foreign and Chinese nationals living or travelling through the city, would all be at risk if they are wanted on the mainland.
Sunday’s protest, which organisers said saw more than a million people take to the streets, in addition to a snowballing backlash against the extradition bill, could raise questions about Ms Lam’s ability to govern effectively.
Official Chinese media has accused “foreign forces” of trying to damage China by creating chaos over the extradition bill.
Human rights groups have repeatedly cited the alleged use of torture, arbitrary detentions, forced confessions and problems accessing lawyers in China, where courts are controlled by the Communist Party, as reasons why the Hong Kong bill should not proceed.
China denies allegations of human rights abuses.