In a shocking revelation, the FBI has confirmed that it is aware of the existence of secret “police stations” run by the Chinese government in several U.S. cities, including New York, where two men were arrested on Monday for allegedly operating one under the direction of an official in China.

According to a report by Safeguard Defenders, a human rights group based in Spain, these “police stations” are part of a global network of more than 100 such units that are used to spy on, harass, and intimidate overseas Chinese who are deemed as dissidents or criminals by Beijing.

The report also linked these stations to the activities of China’s United Front Work Department, a Communist Party body that is responsible for spreading its influence and propaganda abroad.

The FBI director, Christopher Wray, told a Senate hearing on Thursday that he was “very concerned” about this issue and that it violated U.S. sovereignty and law enforcement cooperation processes.

“It is outrageous to think that the Chinese police would attempt to set up shop, you know, in New York, let’s say, without proper coordination,” he said.

Wray also said that the FBI had made several indictments involving the Chinese government harassing, stalking, surveilling, and blackmailing people in the U.S. who disagreed with Chinese leader Xi Jinping.

“This is a real problem and something that we’re talking with our foreign partners about, as well, because we’re not the only country where this has occurred,” he said.

The arrest of the two men in New York was part of an investigation into a scheme known as Operation Fox Hunt, which is a global campaign by China to coerce its citizens or residents abroad to return to face charges.

According to the New York Post, one of the men, Hu Ji, allegedly posed as a Chinese police officer and contacted a target in New York via WeChat, a popular messaging app controlled by China.

He allegedly threatened the target with arrest and imprisonment if he did not return to China and cooperate with an investigation. The other man, Li Minjun, allegedly acted as Hu’s driver and accomplice. Both men face charges of acting as agents of a foreign government without notifying U.S. authorities and conspiracy. They could face up to 15 years in prison if convicted. The FBI said it was also looking into other cases of similar activities by Chinese agents across the country.

Safeguard Defenders said it had identified six other locations where Chinese “police stations” were operating in the U.S., including Los Angeles, San Francisco, Chicago, Houston, Washington D.C., and Boston. It also found stations in Canada, Europe, Africa, Asia, and Australia. The group said these stations were not only used to target fugitives or critics of China, but also to provide administrative services to overseas Chinese, such as renewing drivers’ licenses or passports.

However, it warned that these services could also be used to collect personal information or coerce cooperation from Chinese nationals abroad. China has denied running these overseas stations and claimed they were offices to help Chinese citizens renew documents. Safeguard Defenders said it had evidence that these stations were staffed by public security officers who wore uniforms and badges and displayed signs with police logos.

It also said it had obtained internal documents from some of these stations that showed their involvement in intelligence gathering and influence operations. The group called on the U.S. and other countries to investigate and shut down these stations and to protect their citizens from China’s interference and intimidation. It also urged the international community to hold China accountable for its human rights violations and its attempts to undermine democracy and freedom around the world.