It was the second time this week that China had sought to frame the protests as "terrorism".

China reacted furiously Wednesday to "terrorist-like" attacks on its citizens by pro-democracy protesters during a second day of mass disruptions at Hong Kong's airport that turned violent.

The rallies, which had paralysed one of the world's busiest travel hubs, ended with ugly clashes on Tuesday night that included protesters beating two men.

The Chinese government immediately seized on the attacks to louden its drumbeat of anger and intimidation against the protesters, who have staged 10 weeks of relentless rallies to demand greater freedoms.

"We express the strongest condemnation of these terrorist-like actions," said Xu Luying, spokeswoman at the Hong Kong and Macao Affairs of the State Council, who called the two men who were beaten "mainland China compatriots."

It was the second time this week that China had sought to frame the protests as "terrorism", part of a pattern of increasingly ominous warnings that have raised fears it may deploy force to quell the unrest.

Chinese warnings

China on Monday said there were signs of "terrorism emerging", as state media published a video of armoured personnel carriers driving towards the border with Hong Kong.

US President Donald Trump added to fears Beijing may stage a military intervention to end the unrest, saying on Tuesday his intelligence had confirmed Chinese troop movements toward the Hong Kong border.

"I hope it works out for everybody including China. I hope it works out peacefully, nobody gets hurt, nobody gets killed," Trump said.

The people power movement, which has seen millions take to Hong Kong's streets, was sparked by opposition to a planned law that would have allowed extraditions to mainland China.

It quickly evolved into a much broader campaign for democratic freedoms.

Under a 1997 deal that saw Hong Kong return to China from British colonial rule, the city is meant to have far greater liberties than those allowed on the mainland.

The protesters, who are demanding that China's rulers stop interfering in the city, have enjoyed widespread support throughout most sectors of Hong Kong's society.

But the beating of the two men at the airport on Tuesday, as well as the blocking of passengers from boarding flights, could backfire in terms of maintaining support.

The movement has no public leaders, with protests organised anonymously over social media and chat apps.

Angry, exhausted

One group, which has organised anonymous press conferences featuring protesters, sought Tuesday to address the concerns that the rallies at the airport had gone too far.

"After months of prolonged resistance, we are frightened, angry and exhausted. Some of us have become easily agitated and over-reacted last night," the group said in a statement.

"For this we feel pained and dispirited and would like to express our most sincere apologies."

Demonstrators turned on the two men, fuelled by suspicions within their ranks about undercover police or spies.

The first man was held for about two hours and assaulted 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.

Another 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 -- said the man was a journalist for the paper.

In another ugly scene, a group of protesters ganged up on a policeman and beat him. They stopped their attack when the policeman pulled his gun and pointed it at them, but did not fire.

On Wednesday there were only a handful of protesters at the airport and many flights were operating as scheduled.

Abyss

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 and said the hub was being "pushed into an abyss."

But she once again refused to make any concessions to the protesters.

The United Nations' human rights chief on Tuesday voiced concern over force used against protesters and called for an impartial probe.

However, Trump has said little to support Hong Kong's pro-democracy movement, drawing criticism from both sides of the American political spectrum.

"Trump favours both sides in Hong Kong protests. Hardly a profile in courage," said Nicholas Burns, a former senior US diplomat now at the Harvard University Kennedy School.