Ties between China and TikTok have long been under scrutiny. Some accounts of the app now appear to be pro-North Korea, China's ally.

A report by the Network Contagion Research Institute (NCRI) at Rutgers University says topics important to the Chinese government are given added or less weight depending on them being favorable.

In its conclusion in the report released this month, the NCRI said: “Whether content is promoted or muted on TikTok appears to depend on whether it is aligned or opposed to the interests of the Chinese Government.”