HONG KONG—A standoff between protesters and police at a university here extended into a second night, with police keeping the area on lockdown while refraining from using the lethal force they had threatened, as increasingly militant antigovernment activists battled back.

Late Monday, police allowed a group of high-school principals to enter the Hong Kong Polytechnic University campus after a group of self-appointed mediators—including the former head of the city’s legislature Jasper Tsang—were allowed inside. They said they had an understanding with police to allow those 18 years of age and under to leave without being immediately arrested. The principals emerged early Tuesday with a group of about 30 students, while dozens more began to come out peacefully.

The principals told reporters they understood that authorities would record the identities of students under 18, though police could decide to take legal action at a later date. Police and government officials have urged protesters to give themselves up peacefully for arrest.

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About 100 protesters remain on campus, Chief Executive Carrie Lam said Tuesday. A third of the 600 people who have left PolyU are under 18 and were let go without being arrested. The rest——around 400 people——are adults and were arrested, she said.

Police on Monday afternoon fired tear gas, pepper bullets and water cannon at dozens of black-clad protesters who jumped railings and tried to flee the campus, driving many back in. Scuffles broke out as protesters hurled bricks while holding umbrellas for cover.


Police in riot gear, including members of an elite squad known as the Raptors, made some arrests in close combat, including wrestling to the ground several demonstrators who had fought back. Live video feeds showed a few protesters evading police and running up alleyways and into greenery at the university as they tried to avoid arrest. In another, protesters rappelled down from a nearby bridge to get away on waiting motorbikes. It was unclear how many successfully fled.

At a police blockade line near the university earlier Monday, a woman who said her daughter was trapped inside the campus burst into tears in front of a couple of police officers. “Please let my daughter go,” said the woman, who knelt down to beg. “Or I would jump from a building in front of you.” Shortly afterward, others joined her for an impromptu sit-in.

The university confrontation, which began a week ago and intensified Sunday morning, has marked an escalation in the tactics underlying the protesters’ strategy. What started as a largely peaceful movement more than five months ago before turning violent has recently taken a yet more combative turn.

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In Washington, Secretary of State Mike Pompeo voiced concern Monday for “the deepening political unrest and violence,” reiterating the U.S. view that Hong Kong authorities must address grievances and bring about calm, and that China should remain uninvolved.


Last week, protesters at universities—who include college- and high-school-age activists as well as older demonstrators—began driving the action more. They began stockpiling makeshift weapons and adopting more aggressive tactics in an effort to maintain the movement’s momentum, fighting with police in several districts near campuses. Protesters began using bows and arrows and adopting the sustained use of slingshots as well as more Molotov cocktails.

Late Sunday, police had threatened to use lethal force if necessary to combat attacks from protesters, who at several times during the day hurled volleys of Molotov cocktails. Protesters had gathered at PolyU after a week of clashes at universities, and caused disruptions at the Cross-Harbor Tunnel—a key artery that connects two main parts of the city.

The standoff continued as a law banning people from wearing masks at protests was ruled unconstitutional on Monday by Hong Kong’s High Court. The ruling marks a setback for the government, which had imposed the measure under emergency powers in an attempt to quell the unrest.

A commentary published on Monday by the People’s Daily newspaper, a mouthpiece of China’s ruling Communist Party, said there should be no room for compromise with protesters, adding that Hong Kong’s future had reached a crisis point. It said there would be no toleration of radical, violent activities that challenged the “one country, two systems” principle that governs China’s relationship with semiautonomous Hong Kong.

The entrance to the key Cross-Harbor Tunnel has been disrupted during continuing protests. Photo: dale de la rey/Agence France-Presse/Getty Images

Chinese Defense Ministry spokesman Col. Wu Qian, speaking to reporters at a regional conference of defense officials in Bangkok, cited a Nov. 14 speech by Chinese President Xi Jinping in which he said the president gave “the highest direction of the central government” to end violence and restore order in Hong Kong. He called it the army’s most pressing task in Hong Kong.


Mrs. Lam, Hong Kong’s leader, has stayed mostly out of the public eye during the standoff, though she did visit a police officer who was shot by an arrow during Sunday’s clashes at PolyU. In a Facebook post on Monday, she referred to the protesters as “rioters” and condemned the destruction of facilities in and around campus, as well as the use of Molotov cocktails and bricks.

“The police have made many appeals; whoever is inside the Polytechnic University campus should listen as soon as they can,” Mrs. Lam wrote.

Inside the campus, meanwhile, protesters were trapped inside facilities, a student there said. The surrounding of the campus by police and their use of tear gas on those trying to leave allowed protesters no choice but to hide inside, he said. There were enough food and supplies to last for another day or two, he said. Those inside the university face arrest for rioting if they surrender, and if convicted could face as much as a decade in prison.

Police said Monday that Red Cross volunteers had been allowed to enter PolyU to provide first aid. Previously, police had blocked access for many volunteers hoping to enter the campus to provide aid to the wounded, and photos circulating on social media showed a number of first-aid volunteers had been arrested when trying to leave the campus.

Protesters and Police Clash at Besieged Hong Kong University Antigovernment protesters sought to escape police officers who had surrounded Hong Kong Polytechnic University Hong Kong police detained people near the Hong Kong Polytechnic University on Monday, as a standoff with protesters on the campus extended into a second night. Around a few hundred protesters remained on campus and faced arrest. Dale De La Rey/Agence France-Presse/Getty Images Antigovernment protesters started a large fire in a staircase at the main entrance leading into the Hong Kong Polytechnic University in Hong Kong on Monday. Police have surrounded the campus and called on protesters to give themselves up peacefully. YE AUNG THU/Agence France-Presse/Getty Images Protesters and police on Sunday clashed on a bridge at the Hong Kong Polytechnic University. Anthony Kwan/Getty Images Police detained a woman during a protest in the Tsim Sha Tsui district of Hong Kong on Monday. Kyle Lam/Bloomberg News Protesters run for cover on Monday after riot police fired tear gas toward the bridge they were climbing down to reach the road below as they sought escape from police who had surrounded the Hong Kong Polytechnic University campus. ANTHONY WALLACE/Agence France-Presse/Getty Images Protesters were detained by police near the Hong Kong Polytechnic University in Hong Kong on Monday. ANTHONY WALLACE/Agence France-Presse/Getty Images Police escorted protesters out of the campus of Hong Kong Polytechnic University. Thomas Peter/Reuters A riot police officer firing tear gas at pro-democracy protesters during clashes outside the Hong Kong Polytechnic University on Monday. FAZRY ISMAIL/EPA/Shutterstock Police in riot gear moving through a cloud of smoke as they detain a protester at the Hong Kong Polytechnic University on Monday. Ng Han Guan/Associated Press Protesters reacting as police fire tear gas while they attempt to march toward Hong Kong Polytechnic University on Monday. DALE DE LA REY/Agence France-Presse/Getty Images

“Since a large amount of weapons, including petrol bombs and explosives, remain on PolyU campus, and dangerous chemicals have been stolen from the laboratory, this poses a grave threat to public safety,” the police said. It added that police give “great importance to the injured people at Hong Kong Polytechnic University and the rights of arrested persons.”


The city’s Hospital Authority said 116 people were injured and taken to hospitals on Monday from midnight to 10 p.m. One woman was in serious condition, 44 others stable and 69 discharged. Two were in an unknown condition.

Police said 4,491 people have been arrested since the protest movement began on June 9. Some of those in the latest wave included self-identified medics and some who identified as journalists but couldn’t provide valid credentials.

Police also said they had used live bullets twice, on Sunday night and early Monday morning. In one skirmish, officers fired at a car that attempted to hit a police roadblock.

More skirmishes developed across Hong Kong on Monday and showed few signs of letting up. At 9 p.m., police were firing tear gas and rubber bullets in Jordan, an area in Kowloon near the university, while protesters countered with Molotov cocktails and firebombs.

The umbrella has been a symbol of the continuing protests. Photo: fazry ismail/Shutterstock

Many of them had come out to these districts near PolyU to “save the students,” and could be heard yelling “We’re coming!” while they waded through tear gas and charged at police officers. One man in a dark blue suit, navy tie and white pocket square said he came straight from work because he wanted to support the students.

Loud explosions occurred repeatedly, with big fires in the streets and heavy clouds of smoke hovering over the area. Fliers on social media suggested the roads had been doused with fuel, making the explosions even bigger. Roads were littered with bamboo barricades, umbrellas and garbage, which riot police attempted to clear. Protesters tipped over trash cans, pulling out plastic bottles and filling them with water from the fountain to douse tear-gas canisters.

Protesters also gathered again in Central, the bustling financial district, which last week was engulfed in tear gas.

Meanwhile, the city’s Education Bureau said primary and secondary schools would remain closed. Classes are expected to resume on Wednesday, almost a week after they were initially suspended, the bureau said. Kindergartens and special-needs schools were expected to remain suspended until Sunday.

—Rachel Yeo in Singapore and Nancy A. Youssef in Bangkok contributed to this article.

Write to Natasha Khan at natasha.khan@wsj.com, Joyu Wang at joyu.wang@wsj.com and Steven Russolillo at steven.russolillo@wsj.com