* Cathay Pacific caught in crosswinds of pro-democracy protests
* Protests continue despite warnings from HK leader, Beijing
* 'MeToo' rally also being planned for Wednesday (Writes through)
HONG KONG, Aug 28 (Reuters) - Hundreds of protesters took to the streets of Hong Kong on Wednesday to denounce Cathay Pacific Airways for dismissing crew taking part in or supporting anti-government rallies that have swept the Chinese-ruled city for weeks.
The Hong Kong Confederation of Trade Unions (HKCTU) switched the protest venue, originally planned to be outside the airline's airport headquarters, Cathay City, to the central financial district after police refused permission.
The airport was forced to close two weeks ago after protesters thronged the arrivals hall for days, grounding around 1,000 flights and occasionally clashing with police.
Cathay was targeted for its sacking of 20 pilots and cabin crew and what staff have described as "white terror," a phrase used in Hong Kong and elsewhere to describe anonymous acts that create a climate of fear.
"Revoke termination, stop terrorizing CX staff," proclaimed a black banner in English at the protest site where at least 1,000 gathered before offices closed. "Uphold our freedom of speech."
CX is airline code for Cathay.
The airline has been caught in the crosswinds between authorities in Beijing and protesters who have staged sometimes violent demonstrations since June that have grown into the biggest challenge for authorities in the former British colony since it returned to Chinese rule in 1997.
China has denounced the protests and accused the United States and Britain of interfering in its affairs in Hong Kong. It has sent a clear warning that forceful intervention is possible.
Rebecca Sy, former head of Cathay Dragon's Airlines Flight Attendants' Association, said she was fired without explanation after managers saw her Facebook account.
"We never faced any disciplinary action from the company before. How come now they just terminate me without any valid reason? By simply showing me those printouts of my own private Facebook account?"
Cathay Chief Executive Augustus Tang, who replaced Rupert Hogg after his shock resignation this month, told staff there was "zero tolerance for illegal activities" or policy breaches.
"Right now, we are one of the most watched companies in Hong Kong and indeed the world," he said in a memo seen by Reuters. "The way every single one of us acts, not only at work serving our customers but also outside work - on social media and in everyday life - impacts how we are perceived as a company."
PILOTS, CABIN CREW FIRED
China's aviation regulator demanded Cathay suspend staff from flying over its airspace if they were involved in, or supported, the demonstrations. At least 20 pilots and cabin crew have since been fired, the HKCTU said.
Cathay on Tuesday warned against what it called an illegal protest planned outside Cathay City and reiterated that it had zero tolerance for violence and any staff who took part.
"Cathay Pacific wishes to emphasize that it fully supports the upholding of the Basic Law and all the rights and freedoms afforded by it," it said in a statement, referring to the mini-constitution under which Hong Kong is ruled.
The protests in the Asian financial hub have posed the biggest challenge for Communist Party rulers in Beijing since President Xi Jinping took power in 2012.
Unrest escalated in mid-June over a now-suspended extradition bill that would have allowed people to be sent to mainland China for trial in Communist Party-controlled courts.
It has since evolved into calls for greater democracy under the "one country, two systems" formula under which Hong Kong has been administered since 1997, guaranteeing freedoms that include an independent judiciary.
Hong Kong leader Carrie Lam has not ruled out the possibility her administration could invoke emergency powers.
More protests are planned across Hong Kong in coming weeks, including a general strike on Monday.
Another protest is planned after the Cathay Pacific rally, against what demonstrators say is sexual violence by police.
It has been dubbed the "#MeToo" rally and participants are being encouraged to write "#ProtestToo" on their arms with red lipstick.
Police said they respected the dignity, privacy and rights of people under detention and were aware of online "rumors" that a person had been sexually harassed while in custody.
"We have looked into the records and I must emphasize that such rumors are totally false. Also, we have not received any formal reports or complaints," Tse Chun-chung, chief superintendent of the police public relations branch said in a statement on Tuesday.
Hong Kong is on the verge of its first recession in a decade, weighed down by the protests and a prolonged U.S.-China trade war. (Reporting by Twinnie Siu, Donny Kwok, Felix Tam, Jessie Pang and Farah Master; Writing by Nick Macfie; Editing by Clarence Fernandez)