* Clashes flare around city during strike chaos
* Beijing-backed leader sees "dangerous situation"
* Extradition protests morphed into bigger challenge
* Hundreds of flights cancelled, traffic disrupted (Recasts with new details)
By Donny Kwok and Clare Jim
HONG KONG, Aug 5 (Reuters) - Police fired tear gas at protesters in multiple parts of Hong Kong on Monday after a general strike hit transport and the city's Beijing-backed leader warned its prosperity was at risk.
The protests surpassed earlier shows of dissent in scale and intensity, seemingly stoked by Hong Kong chief executive Carrie Lam's refusal once again to meet any of the protesters' demands, while warning of an "extremely dangerous situation".
What started several months ago as demonstrations over an extradition bill that would have let people be sent to mainland China for trial have grown into a much broader backlash against the city government and its political masters in Beijing.
The protests are the greatest political threat to the former British colony's government since it returned to Chinese rule and one of the biggest popular challenges to Chinese leader Xi Jinping since he came to power in 2012.
Amid extensive disruptions to trains and traffic, tens of thousands of demonstrators fanned out across Hong Kong, spreading pockets of activism to most of its main three regions: Hong Kong island, Kowloon and the New Territories.
Police stations were besieged and roads occupied.
In the evening, a group of men armed with sticks tried to attack the black-clad protesters in the North Point district.
Riot police used tear gas in districts including Wong Tai Sin, Tin Shui Wai, Tai Po, and Admiralty close to the city's government headquarters.
Speaking to the media for the first time in two weeks, Lam remained defiant, rejecting calls to resign, condemning violence and saying the government would be resolute.
She warned that the protests were putting Hong Kong on a path of no return and had hurt its economy.
"They claim they want a revolution and to restore Hong Kong. These actions have far exceeded their original political demands," said a stern-faced Lam, flanked by some, but not all senior members of her administration.
"These illegal acts that challenge our country's sovereignty, and jeopardize 'one country two systems', will destroy the stability and prosperity of Hong Kong," Lam said, referring to the territory's administrative system since 1997, when it was handed back to China.
Demonstrators fear China is gradually encroaching on the island's cherished autonomy.
China's Hong Kong and Macao Affairs Office of the State Council said it would hold another news conference on Tuesday at 2.30 pm (0630 GMT), after one last Monday that announced no new major policy shifts by Beijing despite the upheavals.
"I don't think the government is doing anything to heal society... They provide no solution," said Jay Leung, 20, a university student who joined a protest, dismissing Lam's words as a waste of time.
"I didn't hear anything positive, she just made it worse," added tourism worker Russell, 38.
Demonstrators blocked key roads, including three tunnels, cutting major arteries linking Hong Kong island and the Kowloon Peninsula. In Yuen Long district, a car rammed through a barricade, knocking down protesters.
Commuters struggled to get to work, with many rail and bus services suspended by activists who blocked trains from leaving stations, some by sitting in doorways.
Long lines of traffic snaked across Hong Kong island into the heart of the business centre and hundreds of people were stranded at the airport, where more than 200 flights were cancelled at one point.
Many businesses shut, and workers stayed home.
"Losing a bit of money now is not such a problem, (compared) with losing everything that the freedom of Hong Kong used to stand for," said Mark Schmidt, 49, a restaurant manager who closed on Monday.
In an upmarket shopping mall in Sha Tin, scores of shops were shuttered, including clothing retailer H&M as well as luxury brands Chanel and Dior. Protesters in the shopping centre chanted: "Strike! Support to the end."
Many stores in the bustling shopping district of Causeway Bay were closed for part of the day as well as businesses close to the protests.
Members of the Hong Kong Disneyland Cast Members Union went on strike, as did many lifeguards, forcing authorities to close some beaches and swimming pools.
Police, who some have accused of using excessive force, said the situation was spiralling out of control.
Authorities said 420 people have been arrested over the protests since June 9, while police have fired 1,000 rounds of tear gas and about 160 rubber bullets.
The protesters' demands include a complete withdrawal of the extradition bill and an independent inquiry into government handling of the crisis.
With tourist numbers falling and hotel occupancy rates slumping, the protests are piling pressure on a struggling economy.
IHS Markit's July Purchasing Managers' Index for Hong Kong showed private sector business activity dropped to its lowest level in a decade, also weighed down by the Sino-U.S. trade war.
"I would not be surprised if we see a technical recession - two consecutive quarters of contraction," said Raymond Yeung, chief China economist at ANZ.
The benchmark Hang Seng Index closed down 2.9 percent, falling to its lowest level since January. (Reporting by Clare Jim, Donny Kwok, James Pomfret, Noah Sin, Twinnie Siu, Vimvam Tong, Kevin Liu, Lukas Job, Felix Tam; Writing by Anne Marie Roantree; Editing by Paul Tait, Clarence Fernandez, Simon Cameron-Moore and Andrew Cawthorne)