Since the detention and torture of Hong Kong resident and former U.K consular employee Simon Cheng, fears are growing that some of the thousands of people arrested since the protest movement began may have been sent to mainland China.
In a lengthy account of his interrogation and torture at the hands of state security police in Shenzhen posted to Facebook, the mainland Chinese city just across the border from Hong Kong, Cheng says he glimpsed a group of 10 young people at an interrogation center in Shenzhen.
"I saw around 10 young “criminal suspects” who were receiving interrogations in the center," Cheng wrote. "They are all handcuffed and in orange prisoner vest."
"When I walked through the corridor, I heard one voice shout out from one of the questioning rooms: “raise your hands higher! Didn’t you raise your hands and wave the flags in the protest?!” I guess they were torturing Hong Kong protesters."
Cheng's account has fueled fears that a group of arrested protesters seen in video footage being escorted aboard an East Rail train last week were bound for detention in mainland China.
Pro-democracy political party Demosisto, founded by the leaders of the 2014 pro-democracy movement, tweeted the video with the comment:
"#HKPoliceTerrorists used East Rail Line train, which can reach HK-China border, to transfer arrestees. Nobody knows where the arrestees will be transferred! We mustn't let them go missing!"
Patrick Poon, China researcher for Amnesty International, said the group has received a number of reports of missing arrestees, but that they are nearly impossible to verify, because of a lack of information.
He said the protest movement has demanded an independent inquiry into police violence and abuse of power precisely because the current complaints system advocated by the administration of chief executive Carrie Lam adds up to the police investigating complaints against themselves.
"At present, there is no way to verify these reports with information from multiple sources," Poon said. "The Chinese and Hong Kong governments must explain this. Actually, we must have an independent inquiry."
"It is very worrying, because in the current situation, there is nothing close to the necessary checks and balances," he said. "All that can happen is that the police provide the information with which they are to be investigated, so there is no credibility."
Fifteen threads posted to the LIHKG discussion forum since June detail missing protesters, with concerns that some may have died in custody and their deaths reported as suicide.
A total of 46 people have been informally described as missing on the forum after becoming involved in the protest movement.
According to the Hong Kong Police Force, police have issued 10 notices of missing persons during the past six months, five of whom were aged 15 to 35.
Regarding the video clip of arrestees boarding a train, a police spokesman confirmed that they were indeed arrestees boarding an MTR train requisitioned by police, but said the train only traveled one stop and hadn't taken them to the terminus at Lo Wu on the border.
The anti-extradition movement was sparked by widespread fears that the previously watertight border between mainland China and Hong Kong's separate legal jurisdiction was getting more and more porous, and that the possibility of extradition would put paid to any protections currently enjoyed by Hong Kong residents.
A frontline protester who gave only a nickname A Wai said that was his biggest fear.
"My biggest worry is that the division between Hong Kong and mainland China is getting weaker," he said, citing the cross-border detentions and kidnappings of five Hong Kong booksellers starting in October 2015.
He said Cheng's detention by Chinese police on the Chinese side of a border checkpoint in Hong Kong's West Kowloon high-speed rail terminus was a more recent example.
"Chinese police come to Hong Kong to arrest people whenever they feel like it," A Wai said. "I don't trust the Hong Kong government, either."
"The Hong Kong government won't help us because the suicide or disappearance may have been caused by them," he said. "There's absolutely nothing we can do about it."
"Trying to impose checks and balances on a powerful state machine that is targeting our citizens and even sowing terror among us makes us afraid," he said.
Rumors of renditions
Icarus Wong of Hong Kong Human Rights Monitor group said its members are gravely concerned about the rumors of renditions to mainland China by train, but that Hongkongers are already being detained if they cross the border under their own steam.
"We don't have enough information to judge whether some people have been disappeared or not right now," Wong said. "What we do know is that some people are being intercepted by mainland public security officers when they cross the border into China, and then detained for hours of interviews and interrogations."
"But as to whether there some people have been 'disappeared' or killed, we would really need more information to make judgement," he said.
As of Nov. 21, a total of 5,856 people aged 11 to 83 were arrested during demonstrations in various districts on charges of participating in riots, illegal assembly, causing bodily harm, and assaulting a police officer.
A total of 923 people have been charged. Of those arrested, 332 were under the age of 16, and 2,327 were students, the police public relations bureau said in a statement.
Police on Wednesday were heard warning crowds of lunchtime protesters that they could face arrest if they chant slogans that are "untrue," government broadcaster RTHK reported.
The crowd in Kwun Tong district had been chanting: "Hong Kong hasn't won if tyranny isn't dead."
"It wasn't clear exactly what slogans the police considered to be unacceptable, but media reports suggested the crowd had also accused officers of being rapists and murderers – a claim often heard during the ongoing unrest," the station reported.
Protesters in Kowloon Bay meanwhile called for the immediate disbanding of the police force amid growing anger at what rights groups and overseas governments have termed excessive violence, as well as emerging reports of the torture and sexual abuse of detainees.
Since the movement gripped Hong Kong in early June, state-run Chinese media has tried to characterize the anti-extradition movement, which later broadened to include demands for full democracy and an independent inquiry into police violence, as the work of a handful of pro-independence radicals bent on wreaking havoc at the instigation of "hostile foreign forces."
'Silent majority' myth
Part of the official narrative has been the presumed existence of a "silent majority" who support the government and police, love China, and are angry with the long-running disruption to their daily lives and the use of force by frontline protesters.
But pro-democracy candidates won more than 80 percent of District Council seats after a record three million voters turned out in a ringing endorsement of the broader aims of the pro-democracy movement.
Lam has withdrawn legal amendments that would have allowed extradition to mainland China, but protesters also want fully democratic elections to the city's Legislative Council (LegCo) and for the post of chief executive, an amnesty for the thousands of people arrested since protests began, an end to the use of the term "rioting," and an independent inquiry into police violence.
Lam and her officials have repeatedly ruled out meeting any of the other demands, although analysts said economic concessions were likely in the pipeline in a bid to mollify residents.
Officials at Hong Kong Polytechnic University (Poly U), where police have besieged protesters following violent clashes more than a week ago, have called on police to leave, saying that the blockade should end.
A three-hour search on Wednesday found no sign of protesters anywhere on the campus, but many of the school’s facilities, like classrooms and laboratories, were badly damaged, officials told RTHK.
But police have said they will enter the university on Thursday, and a lone protester read out a statement saying around 20 people are still on the site, and could make a last stand if police enter the campus.
Reported by Tseng Yat-yiu, Tam Siu-yin and Gao Feng for RFA's Mandarin and Cantonese Services. Translated and edited by Luisetta Mudie.