HECTOR RETAMAL/AFP/Getty

Hong Kong International Airport was abruptly closed Monday as pro-democracy demonstrators flooded into one of the world's busiest terminals amid the 10th week of protests in the China-ruled territory that have officials -- and investors -- growing increasingly concerned. 

The airport protests followed images of police firing teargas into a Hong Kong subway station late Sunday, as well as unverified footage of police firing projectiles at demonstrators attempting to escape from a separate station in the city. Both reports underscore the rising tensions between citizens and the China-backed law enforcement, which have been accused of using violent means to quell the demonstrations, which were first triggered by a bill that would have allowed extraditions to mainland China.

Hong Kong airport, one of the world's busiest international hubs, is at a standstill right now as thousands of protesters, many dressed in black, stage a sit-in. After 10 weeks of demonstrations, fears of Chinese military response are mounting. https://t.co/FytifbHKDj pic.twitter.com/LSoGn8UCSi

— Anna Fifield (@annafifield) August 12, 2019

"Hong Kong's radical demonstrators have repeatedly used extremely dangerous tools to attack police officers, which already constitutes a serious violent crime, and also shows the first signs of terrorism emerging," said Hong Kong and Macao Affairs Office of the State Council Yang Guang. "This wantonly tramples on Hong Kong's rule of law and social order."

China's growing irritation with the protest, which have hive more than 10.2% from the Hang Seng index since late June, and tipped the benchmark into negative territory for the year and added to the region's economic pressures as it combats the ongoing trade war with the United States, was evidenced by a report suggesting the People's Armed Police have been assembled in the mainland city of Shenzen. 

Late Friday, China's Foreign Ministry spokeswoman, Hua Chunying, told reporters that the PLA is a "pillar for the city's long-term prosperity and stability,", while its Hong Kong garrison released a video of soldiers drilling with assault rifles, water cannons and armored carriers.

China also labelled the protesters as "terrorists", suggesting either the People's Police, or the People's Liberation Army, could be called in to restore order in the city, which was handed back to China by the United Kingdom in 1997 under a " "one country, two systems" arrangement designed to ensure some form of separation from Beijing rule.

Hong Kong's first and second quarter GDP growth rate held at 0.6% so far this year, but those figures were recorded prior to the intensifying protests in late June. Furthermore, investment rates in the China-ruled territory contracted 12.1% from last year over the second quarter, official data indicated last month, as tensions from the U.S.-China trade war took their toll on exports, freight volumes and tourist spending.