Hong Kong airport has cancelled remaining flights for the second day in a row after protesters took over terminals.
Flight check-in services have been suspended at Hong Kong's international airport, the airport authority says, citing disruptions caused by anti-government protests.
Increasingly violent protests have plunged the Asian financial hub into its most serious political crisis in decades, posing a challenge to the central government in Beijing.
The Airport Authority (AA) halted all flights to and from the airport on Monday, and flag carrier Cathay Pacific Airways Ltd said on Tuesday it had suspended all check-ins.
"Terminal operations at Hong Kong International Airport have been seriously disrupted as a result of the public assembly at the airport today," the AA said, adding that check-in service for departing flights had been suspended since 4.30pm local time on Tuesday.
In a separate statement, Cathay Pacific said: "There is potential for further flight disruptions at short notice".
Lam says protests unleash 'panic and chaos'
A state of "panic and chaos" exists in Hong Kong, the city's embattled leader Carrie Lam says, defying calls to quit as the stock market tumbled, airlines flagged further flight disruptions and anti-government protesters filled the airport.
Unrest has roiled the former British colony for 10 weeks as thousands of residents chafe at a perceived erosion of freedoms and autonomy under Chinese rule.
The increasingly violent demonstrations have plunged the Asian financial hub into its most serious crisis in decades, presenting Chinese leader Xi Jinping with one of his biggest challenges since he came to power in 2012.
For a fifth day, protesters occupied the arrivals hall at the airport, shut down in an unprecedented move on Monday that forced hundreds of flight cancellations.
Beijing likened the demonstrations in Hong Kong to terrorism.
"Take a minute to look at our city, our home," Ms Lam told a news conference on Tuesday at the government headquarters complex, fortified with 1.8m-high water-filled barricades.
"Can we bear to push it into the abyss and see it smashed to pieces?".
As she spoke, the benchmark Hang Seng index hit a seven-month low.
By lunchtime, it had dropped nearly 2 per cent, dragging down markets across Asia.
It has fallen 6 per cent since the protests began in June.
The protests began as opposition to a now-suspended bill that would have allowed extradition to mainland China for those facing criminal charges, but have swelled into wider calls for democracy.
Demonstrators say they are fighting the erosion of the "one country, two systems" arrangement enshrining some autonomy for Hong Kong when China took it back from Britain in 1997.
They want Ms Lam to resign. She says she will stay.
"My responsibility goes beyond this particular range of protest," she said, adding that violence had pushed the territory into a state of "panic and chaos".
"I, as the chief executive, will be responsible to rebuild the Hong Kong economy, to engage as widely as possible, listen as attentively as possible to my people's grievances and try to help Hong Kong to move on."
On Monday, China said the protests had reached a critical juncture, after a weekend of street clashes in which both police and protesters appeared to toughen their resolve.
Police fired tear gas at the black-shirted crowds in districts on Hong Kong island, Kowloon and the New Territories.
A senior Chinese official said "sprouts of terrorism" were emerging in Hong Kong, given instances of violent attacks against police officers.
Hong Kong legal experts say Beijing might be paving the way to use anti-terror laws to restrain the protesters.
Some flights resumed as Hong Kong's airport reopened on Tuesday, but hundreds remained cancelled.
Airport officials warned of further protests and disruptions.
Flag carrier Cathay Pacific urged passengers to postpone non-essential travel on Tuesday and Wednesday.
The airline, whose British heritage makes it a symbol of Hong Kong's colonial past, is also in a political bind.
China's civil aviation regulator demanded it suspends personnel who joined or backed the protests from flights into its airspace, pushing its shares to a 10-year low on Monday and lower still on Tuesday.
Shares in Shenzhen Airport Co Ltd surged 10 per cent, the maximum allowed on the index, buoyed by potential flight diversions.
Flagship carrier Air China said it would add capacity on its Beijing-Shenzhen route, as a result of the disruptions.
UN urges Hong Kong to use restraint
United Nations High Commissioner for Human Rights Michelle Bachelet has urged Hong Hong authorities to exercise restraint and investigate evidence of its forces firing tear gas at protesters in ways banned by international law.
"Officials can be seen firing tear gas canisters into crowded, enclosed areas and directly at individual protesters on multiple occasions, creating a considerable risk of death or serious injury," Ms Bachelet said in a statement on Tuesday.
China's comments on Monday about "sprouts of terrorism" emerging in Hong Kong are not helpful and risk inflaming the situation, her spokesman Rupert Colville told a news briefing.