HONG KONG (Reuters) - Chinese police have made their first statement on the fate of one of five missing Hong Kong booksellers, believed by many to have been abducted by mainland agents, acknowledging widespread concerns but offering no fresh information.

A demonstrator wears a mask depicting Causeway Bay Books shareholder Lee Bo during a protest over the disappearance of booksellers, in Hong Kong, China January 10, 2016. REUTERS/Tyrone Siu

Lee Bo, 65, a dual British and Chinese national and owner of a publisher and bookstore specializing in books critical of China’s Communist Party leaders, disappeared from Hong Kong on Dec. 30.

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.

In a rare but brief letter to Hong Kong media on Friday, police in the southern Chinese province of Guangdong offered no fresh information and did not address their Hong Kong counterparts’ requests for a meeting with Lee, government radio station RTHK reported.

The letter repeated two points earlier released by the Hong Kong police - that Lee had sent a letter stating he went to the mainland on his own accord and that mainland authorities had confirmed to Hong Kong that he was “understood” to be on the mainland, RTHK reported.

“If there is news, we will notify (Hong Kong) in a timely fashion,” it said.

The British government is still waiting for responses to its diplomatic requests for information and access to Lee.

Lee’s wife visited him in a mainland guesthouse last weekend. She issued a statement saying he was healthy and in good spirits, and that he was a witness in an on-going investigation.

The 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.

He surfaced on Chinese state television this month, stating that he had voluntarily turned himself into Chinese authorities last month over a fatal drink driving case more than a decade ago.

As international diplomatic concern intensifies, the European Union on Friday delivered some of its strong criticism yet of China’s human rights record.

In a statement on its website, the 28-nation bloc’s China delegation called recent televised confessions by detained Chinese and European citizens “unacceptable”. It described the disappearance of the booksellers a “worrying trend”.

China’s Foreign Ministry spokeswoman Hua Chunying later described the EU’s criticism as irresponsible and “not constructive”.

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.