Washington — American citizen Min Zin has been legally designated by the U.S. State Department as wrongfully detained by China.

"Secretary Rubio has formally designated U.S. citizen Min Zin as wrongfully detained," Dylan Johnson, assistant secretary of state for global public affairs, said Thursday on X. "We call on Beijing to release all U.S. citizens arbitrarily detained or exit banned in China. The safety and security of U.S. citizens is the State Department's top priority."

China announced Min Zin's arrest in June, with foreign ministry spokesman Lin Jian saying he was being held on suspicion "of engaging in espionage and endangering China's national security," without providing further details.

Min Zin, founder and executive director of the Institute for Strategy and Policy - Myanmar, is the second American academic to be designated as wrongfully detained in recent months. The other American is Dr. Youlin Chen, whose wife said in a statement Thursday she was glad to see the latest designation.

"I am glad to see that Secretary Rubio has designated Min Zin as a wrongful detainee," said Youlin's wife, Dr. Yufang Rong. "It meant a great deal to me when my husband, Youlin Chen, was designated because it means that his freedom is a priority for the Trump Administration. I hope it gives the same comfort to Min Zin and his family."

CBS News has reached out to China's embassy in Washington, D.C., for comment.

The Institute for Strategy and Policy-Myanmar, or ISP-Myanmar, said Min Zin was wrongfully detained on June 3 while traveling to Kunming, China, for an academic workshop. In addition to his role at the institute, he is a PhD candidate in the Travers Department of Political Science at the University of California, Berkeley, according to ISP-Myanmar.

"ISP-Myanmar calls for his immediate and unconditional release," the group says. "Academic and research organizations such as ISP-Myanmar should be able to conduct research freely and without fear of intimidation."

Embassy spokesperson Liu Pengyu told CBS News in June that Min Zin's "legitimate rights have been fully guaranteed."

His arrest took place a few weeks after President Trump attended a summit in Beijing with China's President Xi Jinping and called it an "incredible visit." Xi Jinping is planning to visit the U.S. and Mr. Trump in late September.