WASHINGTON — Eight people have been charged with conspiring to work on China's behalf in a plot involving threatening letters and the use of night vision goggles to surveil and coerce a Chinese family to return to their home country to face charges, according to a US criminal complaint unsealed on Wednesday (Oct 28).

Five of the individuals charged, including an American private investigator hired to help spy on the family, were arrested on Wednesday in New Jersey, New York and California, while the rest are believed to be in China, top Justice Department officials said in a news conference.

The alleged plot was known as Operation Fox Hunt and Operation Skynet, court records show, and it took place between 2016 and 2019.

Its goal was to target Chinese nationals living in foreign countries and intimidate them into returning to China to face charges.

The United States does not have an extradition treaty with China. It does, however, require by law that anyone who is acting on a foreign country's behalf must register and notify the Attorney General's office.

All eight defendants in the case are charged with conspiring to act as illegal agents for a foreign government.

A spokesman from the Chinese embassy did not have an immediate comment in response to the allegations.

"This is the first case of its kind, and I think it is significant," said Acting US Attorney for the Eastern District of New York Seth DuCharme.

"What makes the case really stand out is that it directly involves the efforts of a foreign power to conduct unilateral activity here on US soil, in violation of our laws."

The criminal complaint alleges that the group plotted to target a former Chinese government employee and his wife and daughter, who have been living in New Jersey since 2010.

The alleged harassment the family endured included receiving a threatening note that read: “If you are willing to go back to the mainland and spend 10 years in prison, your wife and children will be all right. That’s the end of this matter!”

The family also received threats on social media, as well as packages that contained letters along with taped video threats.

According to notices posted by China with Interpol in 2012 and 2014, China listed the New Jersey man as a fugitive who is wanted for embezzlement, abuse of power and accepting bribes.

Three of the defendants — Zhu Yong, Hongru Jin, and Michael McMahon — were arrested on Wednesday in New York and New Jersey.

A federal judge in New York on Wednesday ordered McMahon to be released on a US$500,000 (S$682.000) bond secured by a New Jersey property.

During the hearing, the judge declined a request by the government to detain Yong Zhu pending trial, and released him into the custody of his son on a US$120,000 bond.

"I don't understand it because I didn't do anything that is illegal," Yong Zhu said through an interpreter. "I was performing a legitimate profession as a driver."

Two others — Rong Jing and Zheng Congying — were arrested in California. The last three defendants — Zhu Feng, Hu Ji, and Li Minjun — remain at large.

Reuters could not immediately determine who is representing the five people who were arrested.

According to his Linkedin profile, McMahon is a former New York Police Department sergeant who retired from the force in 2003.

An attorney, he now works to help provide investigative support but could not be immediately reached for comment.

Also on Wednesday, the US State Department announced it was designating a US branch of a Chinese government-controlled organisation as a foreign mission and withdrawing from an agreement to promote local-level cooperation between the countries.

The moves, announced by Secretary of State Mike Pompeo, were the latest to curb Chinese activity in the United States in the run-up to next Tuesday's presidential election, in which US President Donald Trump has made a tough approach to China a key foreign policy theme. REUTERS