HONG KONG (AP) — Hong Kong police fired tear gas and high-pressure water hoses against protesters who had massed outside government headquarters Wednesday in opposition to a proposed extradition bill that has become a lightning rod for concerns over greater Chinese control and erosion of civil liberties in the semiautonomous territory.

The afternoon violence marked a major escalation in the semi-autonomous Chinese territory’s biggest political crisis in years. It came after protesters earlier in the day forced the delay of a legislative debate over the bill, which would allow criminal suspects in Hong Kong to be sent for trial in mainland China.

Protesters charge barriers near government buildings in Hong Kong as police fire tear gas https://t.co/xIGavklQIi pic.twitter.com/HHOoKR7kr2 — NBC News (@NBCNews) June 12, 2019

The overwhelming young crowd had overflowed onto a major downtown road as they overturned barriers and tussled with police outside the government building. But when some appeared to have breached the police cordon around offices of the government and Legislative Council in the city state’s Wanchai district, leading to the police response, which also included firing nonlethal projectiles.

Earlier, a curt government statement said the session scheduled to begin at 11 a.m. would be “changed to a later time.” Officials gave no indication of when that would be and Hong Kong leader Carrie Lam canceled a scheduled news briefing.

The delay appeared to have been at least a temporary victory for the bill’s opponents, whose 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.

ASSOCIATED PRESS Protestors surrounded government headquarters in Hong Kong on Wednesday as the administration prepared to open debate on a highly controversial extradition law that would allow accused people to be sent to China for trial.

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. But they are also giving vent to young Hong Kongers alienated by a political process dominated by the territory’s economic elite.

Protesters said they hoped the blockade would persuade Lam’s administration to shelve the proposed amendments to the Fugitive Offenders Ordinance and the Mutual Legal Assistance in Criminal Matters Ordinance.

“We want the government to just set the legislation aside and not bring it back,” said a protester who gave only his first name, Marco, to avoid possible repercussions from authorities.

Another protester, who gave her name only as King, also out of fear of repercussions, said the protest was a watershed moment for Hong Kong’s young generation, who face difficult job prospects and skyrocketing housing prices.

“We have to stand up for our rights or they will be taken away,” she said.

Dressed in black T-shirts and jeans, many protesters appeared undaunted by demands to disperse from police. Protesters clashed with police intermittently throughout the day, occasionally hurling traffic cones and other objects over metal traffic barriers. Police initially responded with pepper spray, which was met with unfurled parasols as used in 2014 pro-democracy protests that became known as the Umbrella Movement.

The demonstrators also appeared mindful of Beijing’s growing use of electronic surveillance such as facial recognition technology to build dossiers on those it considers politically unreliable, with many donning surgical or anti-pollution masks to hide their features, as well as to safeguard against tear gas.

Such protests are never tolerated in mainland China, and Hong Kong residents can face travel bans and other repercussions if they cross the border.

Metal fences, initially set up by Hong Kong police for crowd control, have been torn down by protesters and used to build barricades to block the roads around the Legislative Council building: https://t.co/nu6iHffaW1 pic.twitter.com/BrGwOvUiWF — CNN International (@cnni) June 12, 2019

In a statement read out to reporters, Hong Kong Chief Secretary for Administration Mathew Cheung urged the protesters to clear the streets.

“I would also like to ask the people in this gathering to stay calm and leave the scene as soon as possible and not to commit any crime,” he added.

Under its “one country, two systems” framework, Hong Kong was supposed to be guaranteed the right to retain its own social, legal and political systems for 50 years following its handover from British rule in 1997. However, China’s ruling Communist Party has been seen as increasingly reneging on that agreement by forcing through unpopular legal changes.

The government pushed ahead with plans to present the amendments to the legislature on Wednesday despite a weekend protest by hundreds of thousands of people that was the territory’s largest political demonstration in more than a decade.

Lam has consistently defended the legislation as necessary to close legal loopholes with other countries and territories. A vote is scheduled on June 20.

The number of demonstrators gathered outside Hong Kong's legislature is continuing to swell as thousands protest the controversial #extraditionbill pic.twitter.com/Gw0rX0x4N2 — SCMP News (@SCMPNews) June 12, 2019

The protests are widely seen as reflecting growing apprehension about relations with the Communist Party-ruled mainland, where Xi has said he has zero tolerance for those demanding greater self-rule for Hong Kong.

Critics believe the extradition legislation would put Hong Kong residents at risk of being entrapped in China’s judicial system, in which opponents of Communist Party rule have been charged with economic crimes or ill-defined national security offenses, and would not be guaranteed free trials.

Lam said the government has considered concerns from the private sector and altered the bill to improve human rights safeguards. She said without the changes, Hong Kong would risk becoming a haven for fugitives.

She emphasized that extradition cases would be decided by Hong Kong courts.

Opponents of the proposed extradition amendments say the changes would significantly compromise Hong Kong’s legal independence, long viewed as one of the crucial differences between the territory and mainland China.

Hong Kong currently limits extraditions to jurisdictions with which it has existing agreements and to others on an individual basis. China has been excluded from those agreements because of concerns over its judicial independence and human rights record.

Those in Hong Kong who anger China’s central government have come under greater pressure since Xi came to power in 2012.

.@StateDeptSpox: The U.S. expresses grave concern about the Hong Kong government’s proposed amendments to its Fugitive Offenders Ordinance. pic.twitter.com/pbQ9ViCRsG — Department of State (@StateDept) June 10, 2019

The detention of several Hong Kong booksellers in late 2015 intensified worries about the erosion of Hong Kong’s rule of law. The booksellers vanished before resurfacing in police custody in mainland China. Among them, Swedish citizen Gui Minhai is being investigated on charges of leaking state secrets after he sold gossipy books about Chinese leaders.

In May, Germany confirmed it had granted asylum to two people from Hong Kong who, according to media reports, were activists fleeing tightening restrictions at home. It was the first known case in recent years of a Western government accepting political refugees from Hong Kong.