Five men accused of acting on behalf of the Chinese government have been charged with brazen and wide-ranging schemes to stalk and harass Chinese dissidents in the United States, including by seeking to derail the election bid of a little-known congressional candidate, the Justice Department said Wednesday.

The cases underscore what American officials describe as increasingly aggressive efforts by the Chinese government — sometimes involving the use of hired private investigators — to seek out, silence and threaten pro-democracy activists abroad.

“Authoritarian states around the world feel emboldened to reach beyond their borders to intimidate or exact reprisals against individuals who dare to speak out against oppression and corruption,” Assistant Attorney General Matthew Olsen, the Justice Department’s top national security official, said at a news conference announcing three criminal cases.