BEIJING - A Taiwanese publisher reported missing while visiting Shanghai is under investigation for suspected national security crimes, Chinese authorities said Wednesday.
Li Yanhe, the editor-in-chief of Gusa Publishing, is "under investigation by national security organs on suspicion of engaging in activities endangering national security," Zhu Fenglian, spokeswoman for Beijing's Taiwan Affairs Office, told a press conference.
"The relevant parties will protect (Li's) legitimate rights and interests in accordance with the law," she said.
Activists and Taiwan-based journalists had raised the alarm on Li's disappearance, with dissident Chinese poet Bei Ling writing in a Facebook post last week that Li was believed to have been "secretly detained" in Shanghai while on a visit to see family last month.
Li's Gusa Books has published books on history and politics critical of China's ruling Communist Party, including a history of alleged Chinese oppression in the western region of Xinjiang and a title on Beijing's global propaganda efforts.
China's broadly-worded national security law forbids any engagement in "separatist activities" and "subversion", among other actions deemed threatening to the state.
Chinese authorities had previously jailed Taiwanese democracy activist Lee Ming-che for five years on a national security conviction before his release last year.
In 2015, five Hong Kong booksellers offering gossip-filled tomes about China's leaders vanished -- including one from Thailand -- before resurfacing in mainland custody making "confessions".
Beijing has ramped up pressure on Taiwan since the 2016 election of President Tsai Ing-wen -- who regards the island as an independent nation and not part of "one China" -- including by arresting several Taiwanese nationals.
Taiwan's Mainland Affairs Council -- the island's top China policy-making body -- said last week that it was "offering assistance" to Li's family and insisted the publisher was "safe".
Beijing's confirmation of Li's detention comes a day after Chinese authorities formally pressed secession charges against Taiwanese activist Yang Chih-yuan, leader of a minor political party advocating for the island's formal independence.
China claims self-ruled Taiwan as its territory and has vowed to seize it one day. - AFP