Flights leaving Hong Kong have been disrupted for a second day, plunging the former British colony deeper into turmoil as its stockmarket fell to a seven-month low.
The United Nations High Commissioner for Human Rights has urged Hong Kong to exercise restraint and investigate evidence of its forces firing tear gas at protesters in ways banned under international law.
Ten weeks of increasingly violent clashes between police and protesters have roiled the Asian financial hub as thousands of residents chafe at a perceived erosion of freedoms and autonomy under Chinese rule.
China this week condemned some protesters for using dangerous tools to attack police, calling the clashes "sprouts of terrorism".
Hong Kong legal experts say Beijing might be paving the way to use anti-terror laws to try to quell the demonstrations.
Check-in operations were suspended at 4.30pm local time on Tuesday, a day after an unprecedented airport shutdown, as thousands of black-clad protesters jammed the terminal, chanting, singing and waving banners.
Hong Kong chief executive Carrie Lam became emotional during a news conference in the government headquarters complex, which is fortified behind 1.8m-high water-filled barricades.
"Take a minute to look at our city, our home," she said, her voice cracking.
"Can we bear to push it into the abyss and see it smashed to pieces?"
The protests began as opposition to a now-suspended bill that would have allowed suspects' extradition to mainland China, but have swelled into wider calls for democracy.
At the airport, thousands of protesters gathered in the arrivals hall, as well as some parts of departures, using luggage trolleys to blockade the doors to customs checkpoints.
Floors and walls were covered with missives penned by activists and other artwork.
The scene was peaceful as knots of protesters spoke to travellers, explaining their aims.
"Sorry for the inconvenience, we are fighting for the future of our home," read one protest banner at the airport.
"I think paralysing the airport will be effective in forcing Carrie Lam to respond to us ... it can further pressure Hong Kong's economy," 17-year-old Dorothy Cheng said.
Demonstrators say they are fighting the erosion of the "one country, two systems" arrangement that enshrined some autonomy for Hong Kong since China took it back from Britain in 1997.
They want 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".
As she spoke, the benchmark Hang Seng index hit a seven-month low. It shed more than two per cent, dragging down markets across Asia.
Lam did not respond to questions at a press briefing to clarify if she had the power to withdraw the extradition bill and satisfy a key demand made by the protesters, or if she needed Beijing's approval.
Airport authorities had earlier suspended check-in operations as the fifth day of a sit-in by protesters grew increasingly heated. Crowds continued to swell in the evening.