Blockade, beating, pepper spray on second day of Hong Kong airport chaos

Chaos erupted at Hong Kong's airport for a second day Tuesday as pro-democracy protesters staged a disruptive sit-in that paralysed hundreds of flights, saw police fire pepper spray, and a mainland journalist beaten.

Demonstrators defied warnings from the city's leader who said they were heading down a "path of no return", and US President Donald Trump called for calm, saying his intelligence had reported Chinese troop movements toward the Hong Kong border.

The latest protest led to ugly scenes at one of the world's busiest airports where small groups of hardcore demonstrators turned on two men they accused of being spies or undercover police -- and as desperate travellers pleaded in vain to be allowed onto flights.

Hong Kong's ten-week-long political crisis has seen millions of people take to the streets calling for a halt to sliding freedoms and was already the biggest challenge to Chinese rule of the semi-autonomous city since its 1997 handover from Britain.

But two days of protests at the airport have again raised the stakes for the financial hub.

Beijing is sending increasingly ominous signals that the unrest must end, with state-run media showing videos of security forces gathering across the border.

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 travellers who pleaded to be allowed past.

Vigilantism also broke out when crowds turned on two men suspected of being interlopers.

Police recently disguised themselves as activists to make arrests, a move which has sent paranoia soaring about potential infiltrators.

The first man was held for about two hours before eventually being led away in an ambulance. Riot police briefly deployed pepper spray and batons to beat back protesters while they escorted the vehicle away from the departures hall.

Soon afterwards a second man -- wearing a yellow journalist vest -- was surrounded, zip-tied and then beaten by a small group who accused him of being a spy.

In a tweet, Hu Xijun, the editor of China's state-controlled Global Times tabloid -- which has vociferously condemned the protests -- confirmed the man was a journalist working for the paper.

The man was later driven away in an ambulance after fellow protesters and volunteer medics carried him away.

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.