Protest co-organiser Avery Ng says the fact the Chinese government would neither confirm nor deny its involvement in the disappearances has created widespread fear.
On Monday, Chief Executive Leung Chun-ying said that only local law enforcement agencies have the authority to enforce law in Hong Kong under the Basic Law, and no other law enforcement agencies outside of Hong Kong have such authority.
A duty officer from the Hong Kong Police Public Relations Bureau tells CNN police are still investigating and the case continues to be classified as a missing person case.
“No other law enforcement agencies, outside of Hong Kong, has such authority”, he said. Like the four others who disappeared late previous year, he too is associated with publisher Mighty Current.
On Sunday, a group of lawmakers and activists marched to the central Chinese government’s liaison office in Hong Kong, demanding answers about the missing people. The Chinese words on banner reads “Where is Lee Bo?”
Gui Minhai, owner of the publishing house, went missing while on holiday in Thailand in October.
Mr Lee’s wife said on Saturday her husband told her during a phone call that he was “assisting in an investigation“. “‘The government cares very much about Hong Kong residents” rights and safety’.
Hong Kong’s special status under threat?
She reported him missing to police on Friday and said the call he made to her was from a number in the neighbouring Chinese city of Shenzhen.
The BBC’s Juliana Liu in Hong Kong says some suspect the men’s disappearance is connected to a book the publisher may have been planning about an alleged former mistress of Chinese President Xi Jinping, when he was already married to folk singer Peng Liyuan. “We feel that Hong Kong is not Hong Kong anymore, it is named as Hong Kong only”.
The booksellers specialised in publications critical of the Communist Party government.
Numerous books focus on political intrigue and infighting in the corridors of power, and gossip about the exploits of leaders’ families.
Meanwhile, a separate demonstration has been held in Hong Kong to protest at the appointment of a pro-government official to Hong Kong’s main university.
“We should give time to the police to conduct their investigation”, said acting security secretary John Lee.
In Beijing, foreign ministry spokeswoman Hua Chunying told a regular news conference she did not know about the case, and had “no information”.
A named commentary in the fiercely nationalist Global Times newspaper on Monday accused the bookstore of “making a living by disturbing society on the mainland”.
Bo’s bookstore, Causeway Bay Books – touted as Hong Kong’s most famous bookstore – is now closed, and letters of support and good wishes cover its locked door.
“It is terrifying”, said Albert Ho, a pro-democracy lawmaker.
The International Publishers Association has also expressed “serious concerns” for the publishers. Are they are in mainland China?
Chinese police have no right to operate in Hong Kong, its leader CY Leung has said, amid fears a local bookseller has been detained by mainland authorities.
Mr Ho said it was clear what had happened. There was no record of Lee leaving the city, the SCMP reported, citing an unidentified police source.