Protesters formed a sea of black along roads, walkways and train stations across Hong Kong.

Hong Kong leader Carrie Lam apologised on Sunday as hundreds of thousands of black-clad protesters maintained calls for her to resign over her handling of a bill that would have allowed people to be sent to mainland China for trial.

The chief executive issued the rare apology one day after she indefinitely delayed the extradition bill, which sparked one of the most violent protests in the city in decades.

A government spokesman said that poor government work over the bill had led to "substantial controversies and disputes in society, causing disappointment and grief."

Lam "apologised to the people of Hong Kong for this and pledged to adopt a most sincere and humble attitude to accept criticisms and make improvements in serving the public," the statement added.

Protesters formed a sea of black along roads, walkways and train stations across Hong Kong's financial centre to vent their frustration and anger at the bill and the government's handling of the resulting demonstrations.

Saturday's dramatic suspension of the bill was one of the most significant political retreats by the Hong Kong government since Britain returned the territory to China in 1997, and it threw into question Lam's ability to continue to lead the city.

The protests are also the largest in Hong Kong since Chinese Pressident Xi Jinping came to power in 2012 and pose a challenge to the leadership in Beijing just as they grapple with escalating trade tensions with Washington and slowing economic growth.[ nL4N23N02Z]

Critics say the planned extradition law could threaten Hong Kong's rule of law and its international reputation as an Asian financial hub. Some Hong Kong tycoons have already started moving personal wealth offshore.

"Don't shoot, we're Hongkongers"

Some of Sunday's marchers held signs saying, "Do not shoot, we are HongKonger" - an appeal to police who fired rubber bullets and tear gas at protesters on Wednesday, injuring more than 70 people.

The protest followed one the week before which organisers estimated drew 1 million people and marked the beginning of a week of unrest ahead of the bill, which had been scheduled for debate last Wednesday.

"It's much bigger today. Many more people," said one protester who gave her name as Ms Wong. "I came today because of what happened on Wednesday, with the police violence."

Loud cheers rang out when activists called through loud hailers for Lam's resignation and and the cry "step down" echoed through the streets.

"We want to pressure our government because (they) didn't respond to our first march," said Icy Tang, newly graduated from university in Hong Kong. "So we are coming for the second time - and hope she will listen."

Activist investor David Webb, in a newsletter on Sunday, said if Lam was a stock he would recommend shorting her with a target price of zero.

"Call it the Carrie trade. She has irrevocably lost the public's trust," Webb said.

"Her minders in Beijing, while expressing public support for now, have clearly lined her up for the chop by distancing themselves from the proposal in recent days."

Political crisis

The protests have plunged Hong Kong into political crisis, just as months of pro-democracy "Occupy" demonstrations did in 2014, heaping pressure on Lam's administration and her official backers in Beijing.

Chinese censors have been working hard to erase or block news of the protests, wary that any large public rallies could inspire demonstrations on the mainland.

In a weekly blog post published on Sunday, Hong Kong Financial Secretary Paul Chan sounded a reassuring note about the city's financial position.

"Even if the external environment continues to be unclear and the social atmosphere is tense recently, overall Hong Kong's economic and financial markets are still operating in a stable and orderly manner," he wrote.

In the self-ruled island of Taiwan, which China claims as its own, about 5,000 people rallied outside the parliament building in Taipei with banners saying, "No China extradition law" and "Taiwan supports Hong Kong."

Some of the protesters in Hong Kong also waved Taiwan flags.

"Extensive meddling"

The city's independent legal system was guaranteed under laws governing Hong Kong's return from British to Chinese rule 22 years ago, and is seen by business and diplomatic communities as its strongest asset.

Hong Kong has been governed under a "one country, two systems" formula since then, allowing freedoms not enjoyed in mainland China but not a fully democratic vote.

Many accuse Beijing of extensive meddling, including obstruction of democratic reforms, interference with elections and of being behind the disappearance of five Hong Kong-based booksellers, starting in 2015, who specialised in works critical of Chinese leaders.

Pro-democracy lawmaker Claudia Mo said protests would continue if Lam did not scrap the bill. "If she refuses to scrap this controversial bill altogether, it would mean we wouldn't retreat. She stays on, we stay on," Mo said.

Asked repeatedly on Saturday if she would step down, Lam avoided answering directly and appealed to the public to "give us another chance."

Lam's reversal was hailed by business groups including the American Chamber of Commerce, which had spoken out strongly against the bill, and overseas governments.

The UK Foreign Secretary Jeremy Hunt said on Twitter: "Well done HK Government for heeding concerns of the brave citizens who have stood up for their human rights".

China's top newspaper, the People's Daily, on Sunday condemned "anti-China lackeys" of foreign forces in Hong Kong.

The protests have been the largest in the city since crowds came out against the bloody suppression of pro-democracy demonstrations centred around Beijing's Tiananmen Square on June 4, 1989.

Lam had argued that the extradition law was necessary to prevent criminals hiding in Hong Kong and that human rights would be protected by the city's courts which would decide on any extradition on a case-by-case basis.

Critics, including leading lawyers and rights groups, have noted China's justice system is controlled by the Communist Party, and say it is marked by torture and forced confessions, arbitrary detention and poor access to lawyers.