WASHINGTON — After a participant in the historic Tiananmen Square protests entered a 2022 congressional race in New York City, a Chinese intelligence operative wasted little time enlisting a private investigator to hunt for any mistresses or tax problems that could upend the candidate's bid, prosecutors say.

“In the end,” the operative ominously told his contact, “violence would be fine too.”

As an Iranian journalist and activist living in exile in the United States aired criticism of Iran’s human rights abuses, Tehran was listening too. Members of an Eastern European organized crime gang scouted her Brooklyn home and plotted to kill her in a murder-for-hire scheme directed from Iran, according to the Justice Department, which foiled the plan and brought criminal charges.

The episodes reflect the extreme measures taken by countries like China and Iran to intimidate, harass and sometimes plot attacks against political opponents and activists who live in the U.S. They show the frightening consequences that geopolitical tensions can have for ordinary citizens as governments historically intolerant of dissent inside their own borders are increasingly keeping a threatening watch on those who speak out thousands of miles away.

“We’re not living in fear, we’re not living in paranoia, but the reality is very clear — that the Islamic Republic wants us dead, and we have to look over our shoulder every day,” the Iranian journalist, Masih Alinejad, said in an interview.

The issue has grabbed the attention of the Justice Department, which has built cases against dozens of suspects. Senior FBI officials say the tactics have grown more sophisticated, with countries more willing to cross “serious red lines” from harassment into violence as they seek to project power abroad.

“This is a huge priority for us,” said Assistant Attorney General Matthew Olsen, the Justice Department's top national security official.

The trend is all the more worrisome because of an ever-deteriorating relationship with Iran and tensions with China over everything from trade and theft of intellectual property to election interference.

A leading culprit, officials and advocates say, has been China. The Chinese Embassy in Washington disputed that the country engages in the practice and said in a statement that the government “strictly abides by international law.”

“We resolutely oppose ‘long-arm jurisdiction,'” the statement said.

Yet U.S. officials say China created a program to do exactly that, launching “Operation Fox Hunt” to track down Chinese expatriates wanted by Beijing, with a goal of coercing them into returning to face charges.

A former city government official in China living in New Jersey found a note in Chinese characters taped to his front door that said: “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!” according to a 2020 Justice Department case charging a group of Chinese operatives and an American private investigator.

Though most defendants charged in transnational repression plots are based in their home country, making arrests and prosecutions rare, that particular case led to U.S. convictions of the private investigator and two Chinese citizens.

Bob Fu, a Chinese American Christian pastor whose organization, ChinaAid, advocates for religious freedom in China, said he has endured far-ranging harassment campaigns for years. Large crowds of demonstrators have amassed for days at a time outside his West Texas home in well-coordinated actions he believes can be linked to the Chinese government.

Phony hotel reservations have been made in his name, along with bogus bomb threats to police stating that he planned to detonate explosives. Flyers depicting him as the devil have been distributed to neighbors. He said he's learned to take precautions when he travels.

“I'm not really feeling safe,” Fu told AP.

Wu Jianmin, a former student leader in China’s 1989 pro-democracy movement, was targeted in 2020 by a group of protesters outside his home in Irvine, California.

“They shouted slogans outside my home and made verbal abuses," he said. "They paraded in the neighborhood, distributed all sorts of pictures and flyers, and put them in the neighbors’ mailboxes.”

Last year, the Justice Department charged about three dozen officers in China's national police force with using social media to target dissidents inside the U.S. and arrested two men who it says had helped establish a secret Chinese police outpost in Manhattan's Chinatown neighborhood.

The year before, federal prosecutors disclosed a series of wide-ranging plots to silence dissidents .

Besides the little-known and unsuccessful congressional candidate about whom China wanted to dig up dirt, other victims of harassment in the case included American figure skater Alysa Liu and her father, Arthur, a political refugee who prosecutors say was surveilled by a man who posed as an Olympics committee member and asked them for their passport information.

“We should be under no illusion that somehow these are rogue actors or people that are unaffiliated with the Chinese government,” Rep. Raja Krishnamoorthi, an Illinois Democrat and member of a special House committee on China, said of the Chinese operatives who have been charged.

Alinejad, the Iranian journalist, was targeted even before the Justice Department last year revealed the plot against her involving the organized crime proxies. Prosecutors in 2021 charged a group of Iranians said to be working at the behest of the country's intelligence services with planning to kidnap her.

She remains active as a journalist and activist and says she's determined to keep speaking out. But the details of the crime are chillingly etched in her mind, with the criminal cases laying bare the gravity of the threat.

The FBI disrupted the plot but also encouraged her to move, which she has done. But that also meant saying goodbye to her garden, which had brought her joy as she gave homegrown cucumbers and other vegetables to neighbors.

“They didn't kill me physically, but they killed my relationship with my garden, with my neighbors,” she said.