First admission by mainland Chinese authorities that three men linked to Causeway Bay Books who disappeared in November have been detained

This article is more than 4 years old

This article is more than 4 years old

Chinese police have confirmed for the first time that three of five Hong Kong booksellers who went missing were being investigated for “illegal activities” in China, according to a letter sent to Hong Kong police on Thursday.

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.

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The three men – Lui Por, Cheung Chi-ping and Lam Wing-kee, who were linked to the Causeway Bay Books shop – had had “criminal compulsory measures” imposed on them, Chinese police in the southern province of Guangdong told Hong Kong police.

This was the first indication by mainland Chinese authorities as to the fate of the three since they were reported missing last November. No other details of their location or condition were given.

Hong Kong police referred to the letter from the Chinese police in a statement, but did not make it public in full.

Two other Hong Kong booksellers who also disappeared, Gui Minhai and Lee Bo, are believed to have been abducted or coerced from Thailand and Hong Kong respectively, and taken to China, according to foreign diplomats.

Hong Kong police said China had also given them a handwritten letter from Lee, stating that he was in China. In the letter Lee declined a request by Hong Kong police to meet him. He gave no further details.

However, Hong Kong police said they still wanted to meet Lee as soon as possible and were pressing Beijing for more information on the other three.

No specifics were given on the alleged crimes of Lui, Cheung and Lam, other than that they were suspected of involvement in a case related to Gui, a Swedish passport holder, who made a tearful confession on Chinese television last month to a fatal hit-and-run incident over a decade ago.

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Gui and Lee – a dual British and Chinese national – had been owners of the same publisher and bookstore that specialised in books critical of China’s Communist party leaders.

The British government is still waiting for responses to its diplomatic requests for information and access to Lee. The EU and the US have also expressed concern about the disappearances.

So far, Chinese authorities have made no substantial statements explaining Beijing’s role in the disappearances or how the men ended up in China. China’s foreign ministry has said Hong Kong is China’s domestic affair and “no foreign country has the right to interfere”.

Britain returned Hong Kong to China under agreements that its broad freedoms, way of life and legal system would remain unchanged for 50 years.