The case comes around the same time a Japanese pharmaceutical executive was imprisoned, adding to growing unease even as Beijing tries to court overseas investors.

China has sentenced a Japanese executive to more than three years in prison and blocked a U.S.-based Wells Fargo banker from returning home, the latest in a series of episodes that have made leaders of multinational corporations leery of traveling to China.

Economic policy ministries in China have been trying to persuade multinationals to increase their investment in China. That is an effort that the exit ban and prison sentence are likely to make harder, especially because foreign enthusiasm was already waning. A real estate crash has depressed consumer spending; regulatory obstacles hamper sales in China by foreign companies; and many industries face severe overcapacity.

China has said little about either executive. Eric Zheng, the president of the American Chamber of Commerce in Shanghai, called for the release