US secretary of state Mike Pompeo (Reuters photo)

WASHINGTON: The United States is gravely concerned by the deepening political unrest and violence in Hong Kong , secretary of state Mike Pompeo has said, urging the city's government to address public concerns and China to honour its promises of liberties.

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.

"The United States is gravely concerned by the deepening political unrest and violence in Hong Kong, including the standoff between protesters and police at Hong Kong Polytechnic University and other campuses," Pompeo told reporters at a news conference here on Monday.

The United States has repeatedly called for restraint from all parties in Hong Kong. "Violence by any side is unacceptable," he noted.

Warning that the Hong Kong government bears primary responsibility for bringing calm to Hong Kong, he said unrest and violence cannot be resolved by law enforcement efforts alone.

Stating that the government must take clear steps to address public concerns, Pompeo called on chief executive Carrie Lam to promote accountability by supplementing the Independent Police Complains Council review with an independent investigation into the protest-related incidents.

"As the United States Government has said repeatedly, the Chinese Communist Party must honour its promises to the Hong Kong people, who only want the freedoms and liberties that they have been promised in the Sino-British Joint Declaration, a UN-filed treaty," Pompeo said.

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.

The clashes are some of the worst violence since anti-government protests began in Hong Kong five months ago.

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.

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.

Beijing denies interfering in Hong Kong's affairs and has blamed Western countries for stirring up unrest.

