BBC Chinese recently reported that, according to South Korean Ministry of Foreign Affairs officials, China expelled 32 South Korean missionaries in January and arrested another South Korean citizen in February. It is not yet clear whether this had anything to do with the deployment of the THAAD (Terminal High Altitude Area Defense) missile defense system. The South Korean Ministry of Foreign Affairs reminded its Christian organizations that their activities must follow foreign local laws. In February, China also detained a pastor who is an American citizen. China so far has no explanation of these activities. According to South Korean media, there are over one thousand South Korean missionaries in China and many of them have lent a helping hand to North Koreans to escape to China. In the meantime, Chinese authorities have banned or punished South Korean commercial activities in China (such as events in the entertainment business) as well as South Korean companies.
Source: BBC Chinese, February 11, 2017
http://www.bbc.com/zhongwen/simp/chinese-news-38944081