The United States is "gravely concerned by the deepening political unrest and violence in Hong Kong" as the confrontation between police and protesters has escalated in recent days.
"We've repeatedly called for restraint from all parties in Hong Kong. Violence by any side is unacceptable. The Hong Kong government bears primary responsibility for bringing calm to Hong Kong," U.S. Secretary of State Mike Pompeo said Monday during a press briefing at the State Department.
Pompeo's remarks came amid a dramatic escalation in unrest, with Hong Kong police threatening to fire live bullets if demonstrators did not stop using weapons in the latest anti-government protests.
"Unrest and violence cannot be resolved by law enforcement efforts alone. The government must take clear steps to address public concerns," added the top U.S. diplomat.
Senior U.S. officials have repeatedly called on the Chinese government to honor its promises to the Hong Kong people "who want the freedoms and liberties" that they have been promised in the Sino-British Joint Declaration, a U.N.-registered treaty.
On Monday, Senate Majority Leader Mitch McConnell hit out at China, pointing to leaked documents that "delineate the government's chilling, systematic campaign against ethnic minorities in another supposedly autonomous region, Xinjiang."
"The problem is Beijing's efforts to erect the same kind of sinister, brutal surveillance state in Hong Kong that China is also trying to set up everywhere else," McConnell said in a speech on the Senate floor. "The protesters are not the problem. It is Beijing and the Hong Kong leadership who must de-escalate."
The top Republican in the Senate called on the Trump administration to not solely focus on trade, when it comes to China, but also "make Hong Kong's autonomy a key topic within our bilateral diplomacy."
Polytechnic University siege
Earlier Monday, police tightened the barricade around the Polytechnic University and prevented dozens of students from breaking through police lines.
The president of the Polytechnic University said he has brokered a truce with police that would allow the hundreds of protesters trapped inside the campus to leave peacefully.
Teng Jin-Guang Teng said he received assurances from police for a temporary suspension of the use of force if the protesters do not initiate the violence.
"We have also received permission from the police for you to leave the campus peacefully, and I will personally accompany you to the police station to ensure that your case will be fairly processed," Teng said.
It is unclear whether and when the truce was taking effect.
Dozens of student protesters, however, made another frantic attempt to escape the university that has been surrounded by riot police, as the siege on the campus entered a second day.
Waves of students fled on foot late Monday, running through clouds of tear gas as they attempted to break through police lines.
Threat of lethal force
It was the second concerted attempt by students to flee the urban campus, which has been surrounded by police who have repeatedly warned they will use lethal force.
Live feeds showed riot police chasing down students, some of whom were covered in blood. It was not immediately clear how many were arrested and how many may have escaped the campus successfully.
The clashes raised fears that the siege would end in a deadly crackdown.
Students barricaded themselves on the campus, and several others across Hong Kong, early last week, stockpiling homemade weapons such as petrol bombs, slingshots and bricks.
Early Monday, VOA saw police arrest dozens of students, who were detained with plastic wire ties around their wrists. Some were marched in front of reporters as they were taken away toward waiting police vans.
"I can't imagine this happening in Hong Kong. We are a civilized city and we are witnessing so many uncivilized acts," said a young man nicknamed Ronald, who came out to witness the campus siege firsthand. "We all have something in common and we all want to achieve the same thing.
"In my opinion, (the students) are not really violent. They are acting in response to the police force," he said.
Thousands of riot and other police have surrounded the urban campus of the Hong Kong Polytechnic University for the past day, warning the students to drop their weapons. But a hardcore group showed no signs of surrender. Earlier, police said they were arresting students on riot related charges.
The number of casualties is not clear. Police on Sunday warned they would use lethal force if they continued to be attacked. Local media reports said live rounds were used in several cases.
The clashes are some of the worst violence since anti-government protests began in Hong Kong five months ago.
Escalating protests
Since June, Hong Kong has seen massive, regular demonstrations, which started in opposition to a proposed bill that would have allowed Hong Kong citizens to be extradited to the mainland. The protests quickly morphed into wider calls for democracy and opposition to growing Chinese influence.
A smaller group of hardcore protesters, many of whom are college students, have also increasingly engaged in more aggressive tactics — clashing with police, destroying public infrastructure, and vandalizing symbols of state power. The students have defended the tactics as a necessary response to police violence and the government's refusal to accept their demands.
Hong Kong Polytechnic University is one of at least five campuses where students this week barricaded themselves in, blocking roads and collecting makeshift weapons in case of an attack by authorities. Most of the protesters had left the other campuses by Saturday, though a group of hardcore protesters remained at Polytechnic.
The protests escalated in the past week, following the first death of a protester who fell from a building during clashes between protesters and police.