Police in Hong Kong clashed with throngs of protesters outside government buildings Wednesday as opposition intensified to a proposed extradition bill that would tighten Beijing's control over the semi-autonomous territory.

Hong Kong Chief Executive Carrie Lam blamed the violence on politically motivated protesters she accused of "life-threatening" behavior. Police in riot gear used tear gas and rubber bullets to break up the crowds, which quickly returned when the crackdowns eased. Some threw objects at advancing officers.

Amid the chaos, government officials delayed the opening of debate on the bill, which has drawn massive protests from students and other pro-democracy advocates in the economically free-wheeling city of more than 7 million people.

The legislation, if approved, would allow Hong Kong to extradite suspected criminals to jurisdictions outside the former British colony without a prior agreement – most notably mainland China. It was not immediately clear when formal consideration of the bill would take place.

Lawmaker Charles Mok visited the protest Wednesday, defending the crowd as "well-meaning citizens" exercising freedom of expression.

"I am worried that they (police) might just use force to remove these people and arrest them all," Mok said. "This is not Hong Kong."

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Pablo Wang, a freelance journalist based in Hong Kong, was at the protest for over 9 hours. He told USA TODAY the perseverance of the mostly youthful crowd, who he said were peacefully protesting, was unprecedented in Hong Kong.

“After the tear gas and after the police operation to clear the (area), I left the premises and I saw so many of them still looking at their phones, and trying to reorganize, and looking for a way to go back,” Wang said. "The million dollar question – What is next? I don’t think anyone in Hong Kong knows.”

Man-Kei Tam, director of Amnesty International Hong Kong, accused police of using the angry actions of a small number of protesters as a pretext to use excessive force against the masses.

"The excessive response from police is fuelling tensions and is likely to contribute to worsening violence, rather than end it," the director said. “The ugly scenes of police using tear gas and pepper spray against overwhelmingly peaceful protesters is a violation of international law."

Hong Kong operates under a “one country, two systems” framework that was supposed to include the right to retain its own social, legal and political systems for 50 years following its handover from British rule in 1997.

The U.S. State Department this week expressed "grave concern" over the extradition proposal, saying it could threaten Hong Kong's "special status" with the mainland. That brought a sharp response from Beijing on Wednesday, with Foreign Ministry spokesman Geng Shuang saying no country has a right to interfere in its internal affairs.

"We ask the U.S. side to adopt a fair and objective attitude with regard to the lawful amendment of the ordinances by the Hong Kong SAR government, be discreet in its words and actions and stop interfering in Hong Kong affairs and China's internal affairs in any form," he said.

The legislation was triggered by a homicide case last year. Taiwanese authorities were unable to prosecute a Hong Kong man accused of killing his pregnant girlfriend in Taipei because he fled to Hong Kong. Taiwan's Mainland Affairs Council, in support of Hong Kong's special status, has decried the legislation, however, threatening to post a travel advisory for Hong Kong if the bill becomes law.

More:If Hong Kong extradition bill passes, what will happen?

The protests are the largest since pro-democracy demonstrations closed down parts of the Asian financial center for more than three months in 2014. Some businesses closed for the day, and labor strikes and class boycotts were called.

The protests are a challenge to China’s ruling Communist Party and President Xi Jinping, who has in the past said he would not tolerate Hong Kong being used as a base to challenge the party’s authority.

Michael C. Davis, a fellow with the Washington-based Woodrow Wilson International Center for Scholars, said Hong Kong can expect to see continuing protests as long as the government keeps pushing the bill. Davis, who taught law at the University of Hong Kong until late 2016, also said to expect more arrests, noting the police’s aggression in using tear gas and rubber bullets.

“All of this promises a similarly more determined response from the protestors,” Davis told USA TODAY. “The government has shown no interest in trying to mitigate this evolving situation. If blocked from protesting around LegCo the protesters may resort to strikes and boycotts. The government holds the cards to pull back and reconsider the bill but has shown no inclination to do so.”

On Sunday, hundreds of thousands of demonstrators gathered against the bill in one of Hong Kong's biggest protests in recent history. People of all different backgrounds marched together peacefully until a smaller group clashed with the police outside the government headquarters.

The legislation has caused internal strife within the city, even prompting physical violence when lawmakers for and against the bill battled over access to the chamber.

At a brief news conference, Police Commissioner Stephen Lo Wai-chung called the demonstration a riot. That could spell long jail terms for anyone arrested, adding to concerns that Hong Kong’s government is using public disturbance laws to intimidate political protesters.

“We condemn such irresponsible behavior,” Lo said. “There’s no need to hurt innocent people to express your opinions,” he said, adding that people should not “do anything they will regret for the rest of their lives.”

Police spokesman Gong Weng Chun defended the decision to use tear gas and other non-lethal weapons to quell the demonstration.

“I believe that if our officer is not encountering some threat that they probably may suffer from serious bodily harm or even our officer thinks that their life is being threatened, I don’t think our officer has any necessity to use any kind of force,” he said.

Contributing: Yan Zhang, USA TODAY; The Associated Press