Hundreds braved thunderstorms in Hong Kong on Tuesday for a fresh wave of protests against a proposed extradition bill that would allow people to be sent to mainland China for trial, but the Chinese-ruled city's leader said she would not back down.

Hong Kong Chief Executive Carrie Lam said she would push ahead with the bill despite deep concerns across vast swaths of the Asian financial hub that on Sunday triggered its biggest political demonstration since its handover from British to Chinese rule in 1997.

"When the fugitive extradition bill is passed, Hong Kong will become a 'useless Hong Kong,'" said Jimmy Sham, convener of Civil Human Rights Front, the main organizer of last Sunday's demonstration.

"We will be deep in a place where foreign investors are afraid to invest and tourists are afraid to go. Once the 'Pearl of the Orient' [it] will become nothing."

Activist Jimmy Sham talks to reporters outside the legislative council building in Hong Kong on Tuesday. (Thomas Peter/Reuters)

In a rare move, prominent business leaders warned that pushing through the extradition law could undermine investor confidence in Hong Kong and erode its competitive advantages.

A spokesperson for Global Affairs Canada said in an email to CBC News that it is concerned about the potential effect of the proposals on Canadian citizens in Hong Kong.

"Furthermore, we believe that there is a risk that the proposals could impact negatively on the rights and freedoms set down in the Sino-British Joint Declaration," the spokesperson said, referring to the joint declaration between China and the U.K., which provided blueprints for how Hong Kong would be ruled after its return to China in 1997.

The bill, which has generated unusually broad opposition at home and abroad, is due for a second round of debate on Wednesday in the city's 70-seat legislative council. The legislature is controlled by a pro-Beijing majority.

Riot police, random ID checks

Security was tight around the legislature building, with riot police deployed in some areas. Protesters stood under umbrellas in heavy rain, some singing Hallelujah, as police conducted random ID checks.

An online petition has called for 50,000 people to surround the legislature building overnight into Wednesday.

Scores of young passersby had their bags searched by police and some were detained briefly in a nearby metro station. A police officer on the scene who declined to be named said they were searching for weapons to try to stave off any violence.

The Civil Human Rights Front strongly condemned the searches, saying authorities had made people afraid to participate in peaceful gatherings.

More protests for Wednesday

Strikes and transport go-slows were also announced for Wednesday as businesses, students, bus drivers, social workers, teachers, Christian groups and others all vowed to protest, in a last-ditch effort to block the bill.

Britain handed Hong Kong back to China under a "one-country, two-systems" formula, with guarantees that its autonomy and freedoms, including an independent justice system, would be protected.

But many accuse China of extensive meddling, denying democratic reforms, interfering with local elections and of being behind the disappearance of five Hong Kong-based booksellers, starting in 2015, who specialized in works critical of Chinese leaders.

From right, Hong Kong Secretary for Security John Lee, Hong Kong Chief Executive Carrie Lam and Secretary of Justice Teresa Cheng listen to reporters questions during a news conference in Hong Kong amid protests over a planned extradition bill. (Vincent Yu/The Associated Press)

Beijing denies those accusations and official Chinese media this week said "foreign forces' were trying to hurt China by creating chaos over the extradition bill.

Sunday's protest rally 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.

Nearly 2,000 mostly small retail shops, including restaurants, grocery, book and coffee shops, have announced plans to strike, according to an online survey, a rare move in the staunchly capitalist economy.

Eaton HK Hotel, which is owned by Langham Hospitality Investments and operated by Great Eagle Holdings , said it respected workers' "political stances" and would allow them to rally.

Human rights groups have repeatedly cited the alleged use of torture, arbitrary detentions, forced confessions and problems accessing lawyers in China, where the courts are controlled by the Communist Party, as reasons why the Hong Kong bill should not proceed.

China denies accusations that it tramples on human rights.