Bottles were thrown during pitched battles and at least one officer could be seen with a bloodied face, while some protesters were beaten with batons or wrestled to the ground and taken away.

Earlier on Sunday, protesters of all ages and from all walks of life flooded the streets of Hong Kong in historic numbers in a stunning show of solidarity and defiance against the extradition bill.

Organisers declared the turnout to be more than 1 million, double that of the 2003 mass rally that led to the city’s then leader stepping down.

Such was the size of the crowds that they were still flocking to the rallying point long after the first marchers had left, and the tail end of the rally was still in Causeway Bay as night fell.

Many others trying to join were unable to because of police crowd-control measures, as train stations were swamped and traffic was chaotic with some drivers even leaving their cars on the road.

Organising group Civil Human Rights Front claimed a historic turnout at 1.03 million, while police reduced it to a more conservative estimate of 240,000 at its peak.

At the July 1 rally in 2003, police estimated the number was 350,000 before its peak, while organisers claimed it was more than 500,000. That public backlash against the government’s push for national security legislation prompted then chief executive Tung Chee-hwa to step down.

Mass rally against extradition bill in Hong Kong turns violent

This time, the city’s leader has vowed not to back down, with enough votes promised by her political allies in Legco to pass her bill, which would allow the transfer of fugitives to mainland China and other jurisdictions with which Hong Kong has no extradition deal.

“Will anyone still believe Carrie Lam any more if she continues to claim there is only a small number of people opposing the bill?” said former opposition lawmaker Margaret Ng Ngoi-yee, among the hundreds of pan-democrat leaders and activists at the rally.

Why did Hongkongers join million-strong protest march? It's in their DNA

Describing Sunday’s march as a new start for Hong Kong, she said: “We have so many groups, so many schools, even housewives, new migrants, horse racing fans … so many different groups joined the protest on their own initiative.”

Protesters also chanted slogans demanding Lam’s resignation.

“Down, down, Carrie Lam,” and “No extradition to China,” they shouted.

The chief executive chose to spend her Sunday officiating a ceremony at Ocean Park.

A government source said the extradition bill would still be put before Legco for debate and a vote, regardless of the turnout.

“What needs to be done to achieve justice has to be done. One cannot just let criminals escape justice because we don’t trust the mainland system,” the source said, reiterating the government’s argument the bill was needed to plug a legal loophole that was allowing a Hongkonger accused of murdering his girlfriend in Taiwan to avoid extradition to the self-ruled island.

He pointed out 710,000 people had added their names to a signature campaign to support the bill and their voices could not be ignored.

A government spokesman said it had listened carefully to different views on over the past four months and made two revisions.

The government is expected to table the bill for its second reading on June 12, bypassing the usual process of scrutiny by a bills committee, and hopes to have it passed by the end of the current legislative term next month.

Sea of white washes through city as masses heed call on fugitive bill

Lam and her top officials have repeatedly stressed there are provisions under the law to stop people from being persecuted for political or religious beliefs, and that Hong Kong’s judiciary can play the role of gatekeeper for fugitive transfer requests.

Front convenor Jimmy Sham Tsz-kit said: “It is not the end of the story. If the government continues to refuse to heed the people’s voices, there will be more and bigger protests.”

He said protesters would be mobilised to besiege Legco next in the coming days.

The rally was largely peaceful, except for isolated scuffles and some rogue incidents.

Police had to use pepper spray at one point as several masked protesters ran out onto the road and tried to block traffic outside government headquarters in Admiralty.

Earlier, seven men were arrested for criminal damage, theft, and assault during the march.

Hundreds of diehard protesters remained at the Admiralty finishing point long after the rally officially ended at around 10pm.

Some sat in front of the metal barricade to block the car park entrance to the legislature in a stand-off with police.

Opposition to the bill went global on Sunday, with similar protests being staged in 29 cities in 12 countries and regions, from New York and London to Tokyo and Taipei, mainly by Hongkongers living overseas.

With Beijing officially throwing its weight behind Lam to push the bill, it was unlikely to have a change of heart after Sunday’s rally, according to Lau Siu-kai, a vice-chairman of semi-official think tank The Chinese Association of Hong Kong and Macau Studies.

“The issue now is more than the extradition bill. To the Beijing leaders, it is a showdown between China and foreign influence,” he said, referring to the campaign against the bill by Western business chambers and consulates.

“Unlike the 2003 protest when it was Beijing versus the Hong Kong opposition camp, this time, it is Beijing versus the US and its allies.”

Reporting by Phila Siu, Alvin Lum, Su Xinqi, Rachel Yeo, Shirley Zhao, Chris Lau, Linda Lew, Mantai Chow, Athena Chan, Danny Mok and Ng Kang-chung.