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

The cases, taken together, 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.

One of the cases concerns a local branch of the Chinese Ministry of Public Security, which operated inside an office building in Manhattan's Chinatown neighborhood before closing last fall amid an FBI investigation. The two men charged with establishing the outpost were acting under the direction and control of a Chinese government official, and deleted communication with that official from their phones after becoming aware of the investigation, according to the Justice Department.

The men, identified as "Harry" Lu Jianwang, 61, of the Bronx, and Chen Jinping, 59, of Manhattan, were arrested at their homes on Monday morning. It was not immediately clear if they had lawyers who could comment on their behalf.

At no point did the men register with the Justice Department as agents of a foreign government, U.S. law enforcement officials said. And though the police outpost did perform some basic services, such as helping Chinese citizens renew their Chinese driver's licenses, it also performed a more "sinister" function, including helping the Chinese government locate a pro-democracy activist of Chinese descent living in California, according to the officials.

"New York City is home to New York's finest: the NYPD," U.S. Attorney Breon Peace, the top federal prosecutor in Brooklyn, said at a news conference announcing the arrests. "We don't need or want a secret police station in our great city."