Some Chinese students in Canada accuse Beijing of targeting them and their families back in China with online threats and harassment — part of a campaign to crack down on anti-government dissent abroad.

Ruohui Yang is one of those students. He said he came to Canada in 2015 when he was 15 years old because his parents wanted him to study abroad.

In Canada, he said, he began learning things about his home country — such as details of the 1989 Tiananmen Square massacre — that challenged the Chinese government's version of events.

"In mainland China, we have our very own way of describing this event, this massacre. We just claimed that this is not a massacre, not so much people died," Yang told CBC's The House.

"I start to realize … this [protest] movement got the support of pretty much the entire nation, even officers, police, some from the army, some from the government. And everyone was talking about freedom, democracy, a new start.

"I was really shocked that for someone like me, who's raised under the dictatorship of Communist Party for pretty much my whole life, it's really hard to imagine that there was a time that … was so different and so hopeful."

That hope, coupled with the example of the 2019 demonstrations in Hong Kong against a proposed extradition bill, inspired Yang to take part in pro-Chinese democracy protests in Toronto. He also founded the Assembly of Citizens, a Canada-based pro-Chinese democracy organization.

'They call me a slave'

Yang said that, at first, he hid his identity when demonstrating because he feared reprisals from China.

"I was wearing wigs, a mask, even padding my jacket just to make me look really different," he said.

He eventually shed the disguise and started showing his face in demonstrations. That's when the death threats began.

"I do already receive lots of threatening [messages], lots of swearing words, insults on my different social media accounts," he said.

The persecution didn't end there. He said his activism in Canada also caused his parents — who work for the Communist Party in China — to turn against him.

"They [were] really, really furious about my activities," he said. "They call me a traitor. They call me a slave."

Yang is one of a handful of dissidents who testified this summer before a U.S. congressional committee hearing on China's violations of human rights, including the right to free speech and peaceful assembly.

"The national border cannot stop the Communist Party from spreading fear overseas," Yang told American lawmakers.

A half-dozen other current and former Chinese students who studied in Canada shared similar stories with CBC News.

'Fred' is another member of the Assembly of Citizens. CBC is keeping his real name confidential because he fears retaliation against his family in China.

"I have been bullied, I have been spam-bombed by those people who try to threaten my friends," he said.

"They say I should go to die, I'm a traitor of the Chinese nation, I'm the traitor of the Han people."

WATCH | From Hong Kong to Canada, how activists mobilize online: 

From Hong Kong to Canada, how activists mobilize online

Both pro-democracy protesters in Hong Kong and those in China who want the protests to stop have been deploying advanced technological methods to spread their messages.

'Zion', a recent Concordia University graduate — whose real name is also being withheld by CBC News — also told The House that he believes his social media chat group was infiltrated by the Chinese police.

"There was this one time that I was contacted by one … new member who asked about where I live, what I think about the independence movement of Ganzhou, which is my hometown," Zion said.

He said he traced the number back to a police officer in Ganzhou. After he confronted the mystery user, he said, they deleted their account.

China wants overseas students to 'remain silent': report

In May, Amnesty International released a report on the experiences of Chinese dissidents abroad. The report said many Chinese international students attending foreign universities are living in a climate of fear.

"They feel compelled to self-censor and curtail their social and academic activities and relationships or else risk repercussions from the Chinese state," the report says.

"This atmosphere is the result of the Chinese government's efforts to ensure that the country's overseas students remain silent and disengaged on political issues that are perceived by the government as sensitive."

An organization called the Chinese Students and Scholars Association (CSSA) is active on university campuses across the country.

A 2019 report by the National Security and Intelligence Committee of Parliamentarians (NSICOP) quotes the Canadian Security Intelligence Service (CSIS) describing the CSSA as "an important support mechanism for international students studying abroad [that provides] a social and professional network for students."

But the NSICOP report also reported growing public alarm over the relationship between the CSSA and the Chinese government's embassies and consulates.

"CSSA behaviour may also pose a threat to freedom of speech and assembly," the NSICOP report said, citing previous reports of individuals disrupting on-campus events.

One incident involved a student council election at University of Toronto's Scarborough campus being disrupted. In another case, a speech by an activist critical of the Chinese government's treatment of Uyghurs was disrupted at McMaster University.

McMaster's student union later stripped the CCSA of its official club status over alleged links to the Chinese consulate. 

In both cases, the Chinese embassy denied any involvement.

Embassy calls allegations a 'smear'

In a statement issued to CBC News, the Chinese embassy dismissed the claims of CSSA groups being used to advance the government's political objectives, and of Beijing harassing overseas students' families back home, as "sheer smear and vilification."

The embassy said Chinese students studying in Canada established the CSSA to help each other.

"The Chinese Embassy and Consulates in Canada are obliged to provide appropriate consular protection services to overseas Chinese citizens, including students and scholars, in accordance with law, and urge the Canadian governments, universities, colleges and schools to protect their personal safety, legitimate rights and interests during their stay in Canada," an embassy spokesperson said.

"What the Embassy did was above board and beyond reproach."

Parliament fast-tracked legislation this summer aimed at combating foreign interference through criminal sanctions on deceptive or surreptitious acts and a new foreign influence transparency registry.

'It's our duty'

One former national security analyst says current Canadian law can't do much to protect Chinese students from these acts of harassment.

"If it's some type of pressuring of students, Canada doesn't have a lot of laws in terms of foreign interference that are able to deal with these things," said Dennis Molinaro, who now teaches intelligence history at Ontario Tech University.

"How do you stop China from doing things like pressuring people's families or taking it out on someone's family because of what they do here? That's something that clearly Canada has very little ability to change or influence, at least on its own."

Despite the threats and the anxiety they feel for their families back in China, Fred and the other members of the Assembly of Citizens said they're determined to keep fighting for political reform.

"It's our duty. Many people [of] our age in China have suffered, have sacrificed," he said.

"Even if we cannot see this, we cannot see democracy flourishing on the land of China, we hope that at least we can plant the seed."