Beijing (Reuters) - China will on Monday put on trial a Taiwanese activist, who disappeared while on a visit to the mainland in March, on suspicion of subverting state power, in what court authorities said would be an open trial.

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Lee Ming-che, a community college teacher and human rights advocate, went missing on his March visit but authorities later confirmed he had been detained, straining already-tense ties between the mainland and the self-ruling island.

Lee’s trial will begin first thing on Monday morning, at the Intermediate People’s Court of Yueyang city, in the central province of Hunan, a woman who answered the telephone at the court told Reuters.

Authorities have video-streamed or live-blogged increasing numbers of court proceedings in recent years as part of a push towards judicial transparency.

But rights activists say that in sensitive cases, holding “open” hearings is a tool for authorities to demonstrate state power and that usually the defendant has agreed to an outcome.

Photographs of a billboard announcement of the trial date and time, which circulated online on Friday, were genuine, the woman at the court confirmed.

The announcement said Lee would stand trial alongside another man, Peng Yuhua, who is suspected of the same crime. It is not clear who Peng is or what his relationship to Lee is, if any.

Lee Ching-yu, Lee’s wife, who has been campaigning for his release, was contacted this week by a man who said he was her husband’s lawyer and who told her to come to the mainland for the trial, Taiwan’s Mainland Affairs Council said on Thursday.

The council said the Taiwan government would help her apply for travel documents and arrange lawyers to go with her.

Lee’s case has strained relations between Taipei and Beijing, which have been difficult for decades but particularly tense since President Tsai Ing-wen, leader of Taiwan’s independence-leaning Democratic Progressive Party, took office last year.

Beijing regards the island as a breakaway province and it has never renounced the use of force to bring it back under mainland control.

Proudly democratic Taiwan has shown no interest in being run by Communist Party rulers in Beijing.