* Say it undermines democratic freedoms
* Bill also opposed by some Hong Kong business groups
* HK chief executive vows to press ahead with legislation
Thousands 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 press ahead with the bill despite deep concerns across vast swathes 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, convenor of Civil Human Rights Front, the main organiser of 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."
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.
Beijing-based consultancy Gavecal said some bankers in Hong Kong were reporting that many mainland clients were shifting their accounts to Singapore, fearing they could come under scrutiny in the financial hub.
The bill, which has generated unusually broad opposition at home and abroad, is due for a second round of debate on Wednesday in Hong Kong's 70-seat Legislative Council. The legislature is controlled by a pro-Beijing majority.
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 condemned the searches, saying authorities had made people afraid to participate in peaceful gatherings.
Strikes and transport go-slows were also announced for Wednesday as businesses, students, bus drivers, social workers, teachers and other groups all vowed to protest in a last-ditch effort to block the bill.
The Catholic Diocese of Hong Kong called on the government not to pass the bill "hurriedly", and urged all Christians to pray for the former British colony.
Embattled leader Lam, who warned against "radical action" at the latest protest, is herself a Catholic.
Britain handed Hong Kong back to China 22 years ago 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 since then, including obstruction of democratic reforms, interference with local elections and of being behind the disappearance of five Hong Kong-based booksellers, starting in 2015, who specialised in works critical of Chinese leaders.
Beijing rejects those accusations and official Chinese media this week said "foreign forces" were trying to damage 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, 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.
Many residents of the financial centre, both expatriate and local, are increasingly unnerved by Beijing's tightening grip over the city.
Human rights groups have repeatedly cited the alleged use of torture, arbitrary detentions, forced confessions and problems accessing lawyers in China, where 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.
On Tuesday, New Zealand's Court of Appeal, citing human rights risks, ordered the government to reassess its decision to extradite a man to China to face murder charges.
