0958 GMT August 22, 2019
The new protest came as China sent further signals that the 10 weeks of unrest must end, with state-run media showing videos of security forces gathering across the border, AFP reported.
The crisis, which has seen millions of people take to Hong Kong's streets, was already the biggest challenge to Chinese rule of the semi-autonomous city since its 1997 handover from Britain.
But the two days of protests at the airport, one of the busiest in the world, raised the stakes yet again.
All check-ins were cancelled on Tuesday afternoon after thousands of protesters wearing their signature black T-shirts made barricades using luggage trolleys to prevent passengers from passing through security gates.
Scuffles broke out between protesters and travelers who pleaded to be allowed past.
"I want to shut down the airport just like yesterday so most of the departure flights will be cancelled," a 21-year-old student said.
On Monday a crowd that police said numbered 5,000 filled the building to denounce what they said were violent tactics by police in trying to quell weekend rallies.
Airport authorities in response cancelled all flights on Monday afternoon.
'Path of no return'
On Tuesday morning, the city's leader, Carrie Lam, gave an at-times emotional press conference in which she warned of dangerous consequences if escalating violence was not curbed.
"Violence... will push Hong Kong down a path of no return," she said.
Lam, who faced fierce questioning from local reporters and at one point appeared to be on the verge of tears, appealed for calm.
"Take a minute to think, look at our city, our home, do you all really want to see it pushed into an abyss," Lam said, although she again refused to make any concessions to the protesters.
In an interview with the BBC, Hong Kong's last colonial governor Chris Patten agreed the city was "close to the abyss".
The protests began in opposition to a bill that would have allowed extraditions to the mainland, but quickly evolved into a broader bid to reverse a slide of rights and freedoms in the southern Chinese city.
Authorities in Beijing on Monday slammed violent protesters who threw petrol bombs at police officers, linking them to "terrorism".
On Tuesday state media upped the ante, calling protesters "mobsters", warning they must never be appeased and raising the specter of mainland security forces intervening.
Meanwhile, videos promoted by state media showed Chinese military and armored vehicles appearing to gather in the southern city of Shenzhen, which borders Hong Kong.
The UN's rights chief on Tuesday voiced concern over police force used against protesters, and called for an impartial probe.