Video report by ITV News Asia Correspondent Debi Edward
The proposed legislative measure, which would allow criminal suspects to be extradited to mainland China, has pushed the former British colony to its biggest political crisis in years.
Speaking after the protests, Hong Kong chief executive Carrie Lam said the legislation will help the semi-autonomous Chinese territory protect human rights, but opponents argue that it will have the opposite effect and would instead significantly compromise its legal independence, long viewed as one of its key distinctions from mainland China.
Hong Kong currently limits extraditions to jurisdictions with which it has existing agreements or to others on an individual basis under a law passed before 1997 while it was still a British colony.
China was excluded because of concerns over its poor record on legal independence and human rights.
Ms Lam insisted that the legislation will help Hong Kong uphold justice and fulfil its international obligations.
Safeguards added in May will ensure that the legislation protects human rights, she said.
She said the bill seeks to prevent Hong Kong from becoming a haven for fugitives and is not focused on mainland China, adding that Western democracies have accused Hong Kong of failing to address issues such as money laundering and terrorist financing.
The extradition law amendments would allow Hong Kong to send people to mainland China to face charges, spurring criticism that defendants in the Chinese judicial system will not have the same rights as they would in Hong Kong.
Ms Lam said Sunday’s protest shows Hong Kong’s enduring commitment to its people’s freedoms.
She denied that she is taking orders from the central government in China’s capital.
“I have not received any instruction or mandate from Beijing to do this bill,” she said.
“We were doing it — and we are still doing it — out of our clear conscience, and our commitment to Hong Kong.”
Despite Ms Lam's words, critics believe the legislation would put Hong Kong residents at risk of becoming entrapped in China’s murky judicial system, in which political opponents have been charged with economic crimes or ill-defined national security transgressions.
Opponents say that once charged, suspects may face unfair proceedings in a system where the vast majority of criminal trials end in conviction.
In what was likely Hong Kong’s largest protest in more than a decade, hundreds of thousands of people shut down the heart of the skyscraper-studded city on Sunday, three days before the Legislative Council was set to take up the bill.
People of all ages took part in the march.
Some pushed buggies while others walked with canes, and chanted slogans in favour of greater transparency in government.
The protest was largely peaceful, though there were a few scuffles with police as demonstrators broke through barriers at government headquarters and briefly pushed their way into the lobby.
Police in riot gear used batons and tear gas to push the protesters outside.
Three officers and one journalist were injured, according to Hong Kong media reports.
There was a heavy police presence on downtown streets deep into the night.
Authorities said 19 people were arrested in connection with the clashes.
Opponents of the amendments are largely drawn from Hong Kong’s middle class, who boast high education levels but have had to contend with skyrocketing housing prices and stalemated incomes.
The demonstrations refocused attention on Hong Kong, whose residents have long bristled at what many see as efforts by Beijing to tighten control.
The protests dominated newspaper front pages in a city that allows far more freedom of expression than other parts of China.
In Beijing, Chinese foreign ministry spokesman Geng Shuang said China firmly backs the proposed amendments and opposes “the wrong words and deeds of any external forces” that interfere in Hong Kong’s affairs.
“Certain countries have made some irresponsible remarks” about the legislation, Mr Geng said, without elaborating.
Ms Lam was elected in 2017 by a committee of mostly pro-Beijing Hong Kong elites.
Critics have accused her of ignoring widespread opposition to the extradition law amendments.
Agnes Chow, a prominent Hong Kong activist who opposes the bill, said Ms Lam “ignored the anger of more than a million Hong Kong citizens”.
“Not only me, but I believe most Hong Kong people have felt really angry with Carrie Lam’s response to our rally,” Ms Chow told reporters in Tokyo, where she arrived on Monday to appeal to Japanese media and politicians.
“We still feel very different from China,” said retired public servant Ronny Chan, who was watching a football game in a park in the Wanchai district.
“The politicians in Beijing have no idea about us, and I don’t think they really care.”