Rebecca Sy worked for the airline's regional arm Cathay Dragon and is also a union leader

A flight attendant on Friday accused Cathay Pacific of summarily firing her over Facebook posts linked to Hong Kong's political crisis, adding to concerns about a China-driven witch-hunt to root out pro-democracy supporters at major firms.

The Hong Kong-based airline has been accused of bowing to political and commercial pressure from Beijing by sacking employees in recent weeks for their public support for the massive anti-government movement roiling Hong Kong.

Earlier this month, China's aviation authority ordered Cathay Pacific to stop pro-democracy supporters among its 27,000 staff from working on flights to -- or over -- China, after a general strike drew out some of its workers.

On Friday, Rebecca Sy, who worked for the airline's regional arm Cathay Dragon and is also a union leader, said she was pulled off a rota to fly to China and dismissed the next day on August 21.

Management showed her Facebook posts discussing the political situation, Sy said, but added she was not formally given a reason for her sacking.

"The answer I got was 'I can't tell you why'. This is what I cannot accept," a tearful Sy told reporters, without giving details about the content of the Facebook posts.

"It's not just about my termination. We don't want to lose Cathay, a local Hong Kong airline and its message about the core values of Hong Kong."

"All my colleagues are terrified because of this 'white terror'," she added, using a widely deployed term for Chinese pressure on Hong Kong.

The Hong Kong protests, which have dragged on for nearly three months, started in opposition to a bill that would have allowed extradition to mainland China but soon bled into a wider pro-democracy movement.

Non-violent demonstrations have been held over the last several days after weeks of street clashes between police and protesters.

On Friday night a 'human chain' snaked across the city, with protesters linking hands or holding up mobile phones as they chanted "Free Hong Kong".

Beijing, which is tightening its grip on the semi-autonomous southern city, has reacted to the protests with a mix of propaganda, intimidation and economic threats, casting the protesters as a violent mob and putting the squeeze on companies with Chinese interests.

In its latest PR assault, China's state-run media machine accused the company behind Hong Kong's train network of helping shuttle protesters across the city with an "exclusive" service to avoid police.

The MTR Corporation, which is part-owned by Hong Kong's government, said train services during protests have been to help passengers stuck in the chaos.

'White terror'

Cathay Pacific became the focus of China's vituperative social media after some airline staff joined a pro-democracy strike, supported by the union representing the carrier's flight attendants.

On August 16, Cathay CEO Rupert Hogg suddenly resigned as the hashtag #boycottcathaypacificairline racked up tens of millions of views.

The airline has already fired four members of staff associated with the protests -- including two pilots.

In a statement on Friday, Cathay Pacific's corporate affairs boss, James Tong, did not address the dismissal of flight attendant Sy.

But he said: "Recent weeks have been most challenging for all of our people."

"We are a leading international airline... and therefore we are required to comply with all applicable laws and regulations in the jurisdictions where we operate."

Questions have mounted over whether the airline has a list of pro-democracy activists within its ranks, or if Chinese authorities provide details of Cathay workers it does not want to fly.

Hong Kong is renowned for its business-friendly environment, rule of law and freedom of expression.

But most major Hong Kong companies have deep business ties with China, the world's second-largest economy.

Also on Friday, hundreds of accountants, most in suits and wearing masks, held a rally in support of the anti-government protests as unexpected sectors of Hong Kong society hit the streets.

Some of us "are afraid of being sacked by the company", an accountant from a top firm said, giving her name only as Kim.

"It feels that if we don't walk out today, there won't be a chance for us to walk out in the future."