Hong Kong airport cancelled all flights after thousands of pro-democracy demonstrators occupied the main terminal to denounce police brutality, with Beijing denouncing the long-running protest movement as showing ”sprouts of terrorism”.

Demonstrators flooded the departure hall on Monday following reports that a woman suffered a ruptured eye when she was shot in the face with a bean-bag “bullet”. Signs held by protesters included “shame on police” and “Hong Kong is not safe”.

Passengers were urged to evacuate the building amid rumours that the police would attempt to clear it by force but large numbers of demonstrators remained inside as night fell.

Hong Kong airport authority said in a statement the protest had “severely disrupted” its operations and urged people not to travel to the area.

“All flights have been cancelled,” it added. ”All passengers are advised to leave the terminal buildings as soon as possible. Affected passengers please contact their respective airlines for flight arrangement.”

"Eye for an eye" - Protesters highlight police violence in Hong Kong Show all 13 1 /13 "Eye for an eye" - Protesters highlight police violence in Hong Kong "Eye for an eye" - Protesters highlight police violence in Hong Kong A protester blindfolds herself during the occupation of Hong Kong airport following an incident where riot police allegedly shot a teargas canister into a woman's eye Reuters "Eye for an eye" - Protesters highlight police violence in Hong Kong A protester with her right eye covered lies down in the arrival hall during the occupation of Hong Kong airport Getty "Eye for an eye" - Protesters highlight police violence in Hong Kong A protester holds up an alternative design of the Hong Kong metro system map that marks the locations where police have used teargas against demonstrators AFP/Getty "Eye for an eye" - Protesters highlight police violence in Hong Kong Scores of protesters occupy the arrival hall of Hong Kong airport following an incident where riot police allegedly shot a teargas canister into a woman's eye Reuters "Eye for an eye" - Protesters highlight police violence in Hong Kong A breathing mask is seen on the ground where a protester received medical attention after she was allegedly shot in the eye by riot police Getty "Eye for an eye" - Protesters highlight police violence in Hong Kong Protesters occupy the arrival hall of the Hong Kong airport Getty "Eye for an eye" - Protesters highlight police violence in Hong Kong Blindfolded protesters occupy the arrival hall of Hong Kong airport Getty "Eye for an eye" - Protesters highlight police violence in Hong Kong A protester holds a sign that refers to an incident where riot police allegedly shot a teargas canister into a woman's eye Reuters "Eye for an eye" - Protesters highlight police violence in Hong Kong A protester covers her right eye during the occupation of Hong Kong airport AFP/Getty "Eye for an eye" - Protesters highlight police violence in Hong Kong Protesters occupy the arrival hall in Hong Kong airport Reuters "Eye for an eye" - Protesters highlight police violence in Hong Kong As protesters occupy Hong Kong airport, a demonstrator covers his right eye in reference to an incident where riot police allegedly shot a teargas canister into a woman's eye EPA "Eye for an eye" - Protesters highlight police violence in Hong Kong A protester covers her right eye during the occupation of Hong Kong airport EPA "Eye for an eye" - Protesters highlight police violence in Hong Kong A protester holds up a sign referring to an incident where riot police allegedly shot a teargas canister into a woman's eye AP

Operations later resumed at the airport, authorities said on Tuesday morning, but further delays were expected as staff rescheduled 90 cancelled flights from Monday, with more cancellations expected.

Cathay Pacific, the territory’s flagship airline, confirmed it had cancelled more than 200 flights to and out of Hong Kong on Tuesday.

The action of the protesters raises the stakes as both demonstrators and authorities toughen their positions following 10 weeks of protests across Hong Kong.

“This is as a result of the public assembly taking place at Hong Kong International airport today,” the company added.

“Customers are therefore advised to postpone non-essential travel both today and tomorrow and should not proceed to the airport.”

China’s aviation authority said that in light of the situation in Hong Kong, it will increase transfer capacity in the Greater Bay Area airports.

Protesters entered the terminal carrying banners and placards accusing the Hong Kong police of using excessive force. At least one protester at the airport wore a bandage over her eyes as part of a symbolic protest. The bandage was stained with red and bore the message: “HK Police murders HK citizens.”

Hong Kong is the world’s busiest air cargo port and the eighth busiest by passenger traffic, according to the Airports Council International. It has been filled with anti-government protesters for four days.

In China, the cabinet’s Hong Kong and Macao Affairs Office issued a statement saying the situation in Hong Kong was “beginning to show the sprouts of terrorism” and constituted an “existential threat” to the population of Hong Kong.

“One must take resolute action toward this violent criminality, showing no leniency or mercy,” said the statement, attributed to spokesman Yang Guang.

“Hong Kong has reached an inflection point where all those who are concerned about Hong Kong’s future must say ‘no’ to law breakers and ‘no’ to those engaged in violence.”

China’s People’s Armed Police also assembled in the neighbouring city of Shenzhen for exercises, according to a report in the state-backed Global Times newspaper.

Downing Street said it was “concerned” about violence in Hong Kong and called for “calm from all sides”. In the US, Republican Senate leader Mitch McConnell said any violent crackdown by Chinese authorities against the protests would be “completely unacceptable”.

“The people of Hong Kong are bravely standing up to the Chinese Communist Party as Beijing tries to encroach on their autonomy and freedom,” Mr McConnell tweeted. “Any violent crackdown would be completely unacceptable ... The world is watching.”

Such fears were dismissed by Beijing. ”Hong Kong is China’s Hong Kong and Hong Kong affairs are purely China’s internal affairs,” foreign ministry spokeswoman Hua Chunying said in a statement.

Hong Kong, a former British colony, was returned to China in 1997 after the Communist Party-led government agreed that the city’s democratic freedoms would remain unchanged for 50 years.

However, mass protests erupted in June over an extradition bill that would have allowed Hong Kong residents to be sent to the mainland to stand trial.

The bill was later withdrawn but activists are now demanding the resignation of Hong Kong leader Carrie Lam, democratic elections for her successor, the release of those arrested in earlier protests and an investigation into police use of force.