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Police officers Monday cornered hundreds of student protesters who occupied a Hong Kong university, offering the demonstrators one way out: Drop your weapons and surrender or be met with a hail of tear gas and rubber bullets.

For days, the protesters have held the police off from entering Hong Kong Polytechnic University, fortifying their holdout with homemade fire bombs, giant slingshots, bricks and bows and arrows.

At least 38 people were injured there Sunday, the city's Hospital Authority said, after a bloody battle in which a police officer was struck by an arrow and demonstrators set a police van on fire.

As other protests raged across the city, Hong Kong's High Court struck down a ban on the wearing of facemasks in public. The court found that the October ban violated the territory's mini-constitution, know as the Basic Law.

The Hong Kong protests began in June over legislation, since scrapped, that would have allowed extraditions to mainland China, and have expanded to include a broad range of demands for police accountability and greater democracy.

Running out of weapons and supplies, protesters at PolyU sought to flee the campus, only to find all their routes blocked by a cordon of heavily armed riot police officers.

Despite running out of options, the students fear that following police instructions to "drop their weapons" and leave through one designated exit will result in their arrest.

The protesters, many of them university and high school students, have occupied the campus for a week. On Sunday and well into Monday they clashed with police in one of the most violent confrontations in months.

At least 500 protesters remained on campus by afternoon. By nightfall, about 100 people staged a sit-in in front of the police cordon near the university, including women who appeared to be mothers of trapped protesters.

"Most of the people here are parents," said Claudia Mo, a pro-democracy lawmaker who joined the rally. "They realize once their children get out they will be immediately arrested. They just want to take a look at their kid and see if he or she is OK."

Conditions on the campus have grown increasingly desperate with injured protesters unable to receive treatment, said Owan Li, a student council member. Student leaders said protesters suffered eye injuries and hypothermia after being hit by a dye shot from a police water cannon.

Trying to mediate the stalemate, Jasper Tsang, founder of Hong Kong's largest pro-Beijing political party, arrived at the university late Monday. Tsang said he was willing to accompany protesters to help ensure their safety.

Later, dozens of protesters lined up at the exit and were arrested on rioting charges.

Police said they arranged for Red Cross volunteers to provide first aid, and that the force would assist those who needed to go to the hospital "before further investigation," implying that arrests would wait until after treatment.

Fernando Cheung, a pro-democracy lawmaker, said that some of the young people trapped inside were "close to breaking down."

The police said 154 people were arrested over the weekend, bringing the total number of arrests to 4,491 since June.