British Foreign Secretary Philip Hammond, left, shakes hands with Chinese State Councilor Yang Jiechi in Beijing on Wednesday.

Any abduction of people from Hong Kong to face charges elsewhere would be an “egregious breach” of Beijing’s promises to rule the former British colony, Britain’s foreign secretary said on Wednesday, amid suspicion that several booksellers critical of China’s leaders have been taken by mainland agents.

Lee Bo, 65, a shareholder of Causeway Bay Books and a British passport holder, went missing from Hong Kong last week, though his wife has withdrawn a missing persons report saying he travelled to China voluntarily.

Four other associates of the publisher that specializes in selling gossipy political books on China’s Communist Party leaders have been unaccounted for since late last year.

The disappearances, and China’s silence, have stoked fears of mainland Chinese authorities using shadowy tactics that erode the “one-country, two-systems” formula under which Hong Kong has been governed since its 1997 return to China.

British Foreign Secretary Philip Hammond told reporters at the end of a two-day visit to Beijing that there had been “no progress” on determining the booksellers’ whereabouts after raising the case with Chinese and Hong Kong officials.

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