The US has applauded Hong Kong’s brave protesters as flights were cancelled and mayhem continued after 10 weeks of disruption.

China has also been warned against a violent crackdown, with the stalemate between angry citizens and the government showing no sign of abating.

China has described the peaceful anti-government protests, which have filled the airport for four days, as showing “sprouts of terrorism”, triggering concerns of a possible crackdown.

Flight cancellations have affected Australian travellers with Qantas cancelling at least three flights that had been due to leave on Tuesday from Sydney, Melbourne and Brisbane.

Anyone planning to travel between Australia and Hong Kong has been urged to check with their airline.

Hong Kong is the world’s busiest air cargo port and the 8th busiest by passenger traffic, handling 73 million passengers a year.

The airport authority said it was working with airlines to resume flights from 6am local time on Tuesday.

Protester are seen climbing onto the airport express station in Hong Kong International Airport. Photo: Getty

As citizens continue their determined opposition, US Senate Republican leader Mitch McConnell praised the bravery of protesters standing up to the Chinese government.

He issued a warning to Beijing that any violent crackdown 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 wrote in tweet on Monday.

“Any violent crackdown would be completely unacceptable … The world is watching.”

The people of Hong Kong are bravely standing up to the Chinese Communist Party as Beijing tries to encroach on their autonomy and freedom. Any violent crackdown would be completely unacceptable. As I have said on the Senate floor: The world is watching. https://t.co/5VPm5P4PfB

— Leader McConnell (@LeaderMcConnell) August 12, 2019

Canadian Prime Minister Justin Trudeau said he was extremely concerned about events in Hong Kong and urged Chinese authorities to handle the protests there with tact.

“We certainly call on China to be very careful and very respectful in how it deals with people who have legitimate concerns in Hong Kong,” Mr Trudeau told a news conference in Toronto on Monday.

Increasingly violent demonstrations in Hong Kong have plunged the Chinese-ruled territory into its most serious crisis in decades, presenting Chinese leader Xi Jinping with one of his biggest popular challenges and raising fears of direct intervention by Beijing.

Some Hong Kong legal experts say official descriptions of some protesters’ actions as “terrorism” could lead to the use of extensive anti-terror laws and powers against them.

Protester are seen walking in the field near Hong Kong International Airport. Photo: Getty

China’s People’s Armed Police have assembled in the neighbouring city of Shenzhen for exercises, the Chinese state-backed Global Times newspaper said.

US President Donald Trump, who has been seeking a major deal to correct trade imbalances with China, drew criticism this month after he described the Hong Kong protests as “riots” and said they were a matter for China and Hong Kong to deal with as the territory was part of China.

On Monday a senior Trump administration official and a State Department spokeswoman urged all sides to refrain from violence, while stressing support for democracy.

The senior official reiterated Trump’s remark that it was a matter between Hong Kong and China, “with the understanding that ‘they’re looking for democracy and I think most people want democracy’.

“Societies are best served when diverse political views are respected and can be freely and peacefully expressed. The United States urges all sides to refrain from violence,” the official said, speaking on condition of anonymity.

Passengers have been impacted by protests at Hong Kong Airport. Photo: Getty

A State Department spokeswoman repeated calls for Beijing to adhere to its commitments to allow Hong Kong a high degree of autonomy after its 1997 handover from British rule.

She said it was important for the Hong Kong government to respect freedoms of speech and assembly

“We condemn violence and urge all sides to exercise restraint, but remain staunch in our support for freedom of expression and freedom of peaceful assembly in Hong Kong,” she said.

“The ongoing demonstrations in Hong Kong reflect the sentiment of Hongkongers and their broad concerns about the erosion of Hong Kong’s autonomy,” she added.

“Freedoms of expression and peaceful assembly are core values that we share with Hong Kong; these freedoms must be vigorously protected.”

A spokesman for British Prime Minister Boris Johnson said on Monday that Britain was concerned about the latest violence in Hong Kong and called for calm from all sides.

-AAP