The United States has called on China to clarify the status of five missing Hong Kong booksellers, saying the case raised serious questions about China's commitment to Hong Kong's autonomy under the one country, two systems framework.
The booksellers, including Lee Bo, 65, a dual British and Chinese national and owner of a publisher and bookstore specialising in books critical of China's Communist Party leaders, are believed by many to have been abducted by mainland agents.
US State Department spokesman John Kirby told a regular news briefing the United States was "deeply concerned".
"These cases ... raise serious questions about China's commitment to Hong Kong's autonomy under the one country, two systems framework, as well as its respect for the protection of universal human rights and fundamental freedoms," he said.
"We urge China to clarify the current status of all five individuals and the circumstances surrounding their disappearances and to allow them to return to their homes."
The British government is still waiting for responses to its diplomatic requests for information and access to Lee, who disappeared from Hong Kong on December 30.
Lee's wife visited him in a mainland guesthouse on January 23 and issued a statement saying he was healthy and in good spirits, and that he was a witness in an investigation.
Four other booksellers are believed to be still in mainland detention, including Swedish national Gui Min-hai, who disappeared from the Thai resort town of Pattaya last October.
Gui surfaced on Chinese state television last month, stating he had voluntarily turned himself into Chinese authorities over a fatal drunken driving case more than a decade ago.
The disappearances have prompted fears that mainland Chinese authorities may be using shadowy tactics that erode the one-country, two-systems formula under which Hong Kong has been governed since its return to China from British rule in 1997.
Britain handed Hong Kong back to China under agreements that its broad freedoms, way of life and vaunted legal system would remain unchanged for 50 years.