Chaos scenes erupted in Hong Kong, with protesters arresting several people including a Chinese mainland journalist.
City managing director Carrie Lam warned that Hong Kong was "on the brink of no return".
Hong Kong airport was forced to cancel all flights for the second consecutive day after the protesters stormed the international airport terminals.
The situation has been labeled as a "disaster" for Hong Kong.
Increasingly violent protests have precipitated the Asian financial hub in its most serious political crisis for decades, posing a challenge to the central government in Beijing.
The last protest led to bad scenes, when small groups of hardcore demonstrators turned on two men who accused themselves of being spies or undercover cops – and as desperate travelers they asked in vain to be admitted to the flights.
The 10-week political crisis in Hong Kong, in which millions of people took to the streets demanding to stop mobile freedoms, was already the biggest challenge to the Chinese domination of the semi-autonomous city since its handover from Great Britain in 1997.
But two days of protests at the airport again raised the stakes for the financial hub.
Beijing is sending more and more threatening signals that the unrest must end, with state-run media showing videos of security forces gathering across the border.
All check-ins were canceled Tuesday afternoon after thousands of protesters in their signed black shirts made barricades using baggage carts to prevent passengers from passing through security gates.
Scribbles erupted between protesters and travelers and vigilantism occurred when the protesters rushed in two men.
Recently the police disguised themselves as activists to make arrests, a move that caused paranoia to rise among the protesters.
The first man was held for about two hours before being taken away in an ambulance. Riot police briefly deployed pepper spray and batons to repel protesters while escorting the vehicle away from the departure hall.
Another man, wearing a yellow reporter jacket, was surrounded, zipped up and then beaten by a small group who accused him of being a spy.
In a tweet, Hu Xijun, director of Chinese state control Global Times tabloid – which loudly condemned the protests – confirmed that the man was a journalist working for the newspaper.
The man was later taken away in an ambulance after protesters and volunteer doctors took him away.
At the beginning of Wednesday, most of the protesters had left and the South China Morning Post reported that the airport authority had obtained an injunction to remove the protesters, although it was not clear how it would be applied.
In a statement just after 5:00 pm local time, the flagship Cathay Pacific said it was forced to suspend check-in services.
"Customers are encouraged to postpone non-essential journeys from Hong Kong on Tuesday 13th August and Wednesday 14th August and should not proceed at the airport," the airline said.
Yesterday, Cathay Pacific was forced to cancel over 200 flights while the South China Morning Post reported up to 300 flights had been canceled in total.
Previously, the airport authority has declared to suspend all flights departing at 16.30.
"The terminal operations at Hong Kong International Airport were severely disrupted as a result of today's public airport meeting," said the airport authority.
After filling the arrivals hall, the protesters poured into the departures area despite the increased security measures designed to keep them out.
The images of the airport showed dozens of protesters lined up for luggage carts until the departure doors were blocked this afternoon.
"This is a disaster for Hong Kong that will cost tens of millions of dollars," Geoffrey Thomas, editor-in-chief and chief executive of AirlineRatings.com told CNN.
The airport contributes 5% to Hong Kong's GDP, directly and indirectly, added Hong Kong secretary of transport, Frank Chan.
Travelers lucky enough to have completed their trials could operate.
Today is the second consecutive day that thousands of protesters have upset one of the busiest airports in the world.
It is the fifth consecutive day that the demonstrators managed to block the arrival and departure halls of the airport.
On a loudspeaker, the airport authority stated that it did not expect incoming flights to be affected, even though dozens of incoming flights had already been canceled.
Some flights were able to depart and land on Tuesday, one day after the cancellation of more than 200 flights.
For days the public was advised not to come to the airport.
CLOSE TO SHOOT
A video from inside the airport shows how the police are terribly close to shooting demonstrators in one of the major transport hubs in the world.
A journalist who filmed the incident said he was "amazed that no one was killed" while the violence increased.
Wall Street newspaper reporter Mike Bird captured a moment in the video in which a policeman pulled out a gun.
In the video, an officer apparently only enters the part of Terminal 1, from which the Cathay Pacific flights depart, and brings a demonstrator to the ground before lifting and then lowering the baton.
A group of other protesters proceed to surround the official. Use his stick before it is removed and then hit repeatedly with it. The officer then draws his handgun and points it at the protesters who promptly escape from him before other officers come to the aid of the policeman.
Bird said the officer "pulled the gun and pointed at the protesters" after being beaten. "Amazed nobody killed here tonight," he said on Twitter.
The situation calmed down after a few hours without the violence getting worse and the crowd cleared, Reuters said.
A COUNTRY, TWO SYSTEMS
The action followed an unprecedented shutdown of the airport on Monday. The Hong Kong airport authority stated that the operations were "severely interrupted" on Tuesday and that the departing passengers were unable to reach the immigration counters.
The protesters say they are fighting against the erosion of the "one country, two systems" provision that has established a certain autonomy for Hong Kong since China took over from Great Britain in 1997.
While Hong Kong is a sovereign part of China, the former colony has significant differences from the mainland, including separate legal and political systems, distinct currency, national sports teams and greater tolerance for freedom of expression.
Hong Kong also retains many of its pre-colonial features, including driving on the same side as Great Britain and Australia, but not China, preserving many place names and British statues of British monarchs and dignitaries.
These two different systems should remain in place for at least 50 years.
However, in recent years Beijing has sought to erode these freedoms through changes to the law, attempts to disallow politicians in favor of independence to take place in the region's parliament and even the disappearance of booksellers critical of the Party leadership Communist.
The increasingly violent clashes between police and protesters have roasted the Asian financial hub. The Hong Kong stock market fell to a seven-month low on Tuesday.
UN Human Rights Commissioner Michele Bachelet urged the Hong Kong authorities to exercise restraint and investigate the evidence of their forces firing tear gas at protesters in ways prohibited by international law. China responded by saying that its comments sent the wrong signal to "criminal criminals".
Some travelers at the city's airport expressed sympathy for the protesters.
"I understand the basics of the protest and have understood: it is freedom and democracy and it is incredibly important," said Pete Knox, a 65-year-old Englishman traveling to Vietnam.
Others were in conflict. Chun-sun Chan, 46, trying to return home to her two children in the UK, said she had feelings for the protesters "but I can't reconcile with myself if this is the right way to do it".