BEIJING (AP) — China has confirmed it is holding three Taiwanese on suspicion of committing subversion or other crimes against the Chinese state, part of a trend that has prompted a travel warning from the island's government.

Spokesman for the Cabinet's Taiwan Affairs Office Ma Xiaoguang told reporters Wednesday that the three were suspected of carrying out activities harmful to national security. He said their cases had already entered the trial stage and their families had been contacted.

Taiwanese reports have identified the three as Tsai Chin-shu, chairman of an organization promoting exchanges between China and Taiwan; Taiwanese activist Lee Meng-chu; and retired professor, Shih Cheng-ping.

Another Taiwanese activist, Lee Ming-che was sentenced to five years in prison in November 2017 on the charge of subversion of state power.