Two men were arrested Monday on charges that they helped establish a secret police station in New York City on behalf of the Chinese government, and about three dozen officers with China's national police force were charged with using social media to harass dissidents inside the United States, authorities said Monday.

The cases are part of a series of Justice Department prosecutions in recent years aimed at disrupting Chinese government efforts to locate in America pro-democracy activists and others who are openly critical of Beijing's policies and to suppress their speech.