Clashes broke out shortly after 3:00 pm (0700 GMT) -- the deadline protesters had given for the government to abandon the controversial bill.

Rows of riot police were quickly outnumbered by protesters -- many wearing face masks, helmets or goggles -- who gathered in the centre of the city ahead of a scheduled debate in the city's legislature.

By late morning, with crowds swelling and major roads blocked by throngs of protesters, officials in the Legislative Council (Legco) said they would delay the second reading of the bill "to a later date".

In tense scenes echoing the Occupy movement in 2014 that shut down swathes of the city for months, people flooded major roads and junctions, dragging barricades onto highways and tying them together. Others plucked loose bricks from pavements.

After the deadline expired, protesters broke into the forecourt of the Legco offices in a bid to breach the building, and demonstrators were seen throwing missiles including metal bars at riot police.

Police beat back umbrella-wielding demonstrators first with batons and pepper spray, then with tear gas.

'Million' march

Organisers of a gigantic march in the city on Sunday said more than a million people turned out to voice their objections to the proposed law, which would allow Hong Kong to send suspects to other jurisdictions around the world-- including China.

But the record numbers failed to sway Hong Kong's pro-Beijing leader Carrie Lam, who has rejected calls to withdraw the bill.

Matthew Cheung, the city's chief secretary, on Wednesday called on demonstrators to withdraw, in the first official reaction to the latest protests.

"I also urge citizens who have gathered to show restraint as much as possible, disperse peacefully and do not defy the law," he said in a video message.

Many opponents are fearful the law would entangle people in the mainland's opaque courts, leaving them vulnerable to a justice system seen as acting at the behest of the Chinese Communist Party.

More than 100 Hong Kong businesses said they would close on Wednesday in a gesture of solidarity with the protesters, and the city's major student unions announced they would boycott classes to attend the rally.

A string of other prominent unions in the transport, social work and teaching sectors either followed suit or encouraged members to attend, while a bus driver union said it would encourage members to drive slowly to support protests.

"It's the government who has forced people to escalate their actions, so I think it's inevitable for the fight this time to get heated," said 21-year-old protester Lau Ka-chun.

 

'Hong Kong will bleed'

News of the postponed debate did not deter crowds swelling throughout Wednesday.

"It's not enough to delay the meeting," said student Charles Lee, 23.

"Stalling is not our ultimate goal. We need them to consider scrapping it...

Clashes are unavoidable if they adopt this attitude towards their citizens."

Lawmakers had been due to debate the bill on Wednesday morning in the city's legislature, which is dominated by Beijing loyalists, with a final vote expected on June 20.

It was not announced when the next meeting on the bill would be held.

"The only responsible thing to do now is for Carrie Lam to withdraw the evil bill, or at least to shelve it in order to solve the crisis," said pro-democracy lawmaker Fernando Cheung.

"Because the situation is very tense, if she forces it through and asks the police to use violence, I'm afraid Hong Kong's children will be hurt, will bleed."

Hong Kong's leaders say the proposed law is needed to plug loopholes and to stop the city being a sanctuary for fugitives, and that safeguards are in place to ensure that political critics of Beijing will not be targeted.

But many Hong Kongers have little faith in the government's assurances after years of heightened fears that a resurgent Beijing is trying to quash the city's unique freedoms and culture -- despite a 50-year agreement between Hong Kong's former colonial ruler, Britain, and China that means the city is guaranteed freedoms unseen on the Chinese mainland.

Western governments have also voiced alarm, with the US this week warning the bill would put people at risk of "China's capricious judicial system".

Beijing hit back on Tuesday, with a foreign ministry official saying China "resolutely opposes interference in Hong Kong affairs".

Hong Kong's stock market sank more than 1.8 percent amid the city-wide turmoil, making it the worst performer in Asia on Wednesday. (AFP)