The United States is "disturbed" by reports of the disappearance of five Hong Kong booksellers from the Chinese semi-autonomous city, a US State Department spokesman has said.
The missing men all worked for Mighty Current, known for books critical of Beijing, which closely monitors and controls dissenting voices.
The men are feared to have been detained by Chinese authorities, adding to growing unease that freedoms in the former British colony are being eroded.
"We are disturbed by reports of the disappearances of five people associated with the Mighty Current publishing house and we share the concern of the people of Hong Kong regarding these disappearances," State Department spokesman John Kirby said yesterday.
"We're following the issue closely," he said.
Kirby made reference to a January 4 statement by Hong Kong's chief executive Leung Chun-ying "expressing concerns about the potential implications of this case, and we share those concerns."
Pro-democracy lawmakers, activists and residents fear that Beijing is trampling the "one country, two systems" deal under which Hong Kong has been governed since it was handed back by Britain to China in 1997.
The two sides agreed Hong Kong was to preserve its freedoms - which include freedom of speech - and way of life for 50 years. Chinese law enforcers have no right to operate in the city.
In 2014, tens of thousands of protestors brought parts of Hong Kong to a standstill for more than two months after Beijing imposed restrictions on candidates for the city's next leader.
