While visiting relatives in the Chinese province of Xinjiang last April, Montrealer Arkin Kurban learned through his brother, who worked in government there, that the internal police were looking for him. Even though Mr. Kurban had lived outside the country for more than 15 years and held a Canadian passport, he thought it wise to go to the police station. He did not want any future trouble for him or his family.

Authorities spent 10 hours in an office trying to extract a confession of political subversion from Mr. Kurban, who is a Uyghur, part of a largely Muslim ethnic minority in China that speaks a Turkic language. "You can't do this," he recalled saying. "I'm a Canadian citizen," at which point the interrogating officer threw his passport across the room.

Mr. Kurban is one of six Uyghur-Canadians who reported similar stories to The Globe and Mail, establishing a pattern over the past three years of Chinese enforcement officials who dismiss claims of Canadian citizenship while detaining, blackmailing or even bribing former citizens to spy in their adopted country.

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In Mr. Kurban's case, he told authorities he had helped organize a reception for the World Uyghur Congress in 2008, and police said they would release him on the condition that he monitor community members back in Montreal. He agreed, and was set free. As late as November, officers called him in Montreal for reports. He said he never gave up any information.

Such stories point to the possible infringement on the rights of Canadians and a disrespect of Canadian sovereignty. Details of the incidents cannot be confirmed, but they broadly fit a pattern of interference and do not surprise Canadian officials familiar with the Chinese file.

"Reports of alleged 'foreign interference' in Canada are serious allegations that are referred to the appropriate Canadian officials for follow-up," Diana Khaddaj, spokeswoman for the Department of Foreign Affairs and International Trade, wrote in an e-mail. "We urge China to implement and adhere to international standards on human rights and the rule of law."

When asked about the allegations of interference, Wang Wentian, minister-counsellor at the Chinese embassy in Ottawa, wrote in an e-mail: "I do not believe this groundless story at all."

Canada's Tibetan community has voiced similar complaints about pressure to monitor their own people, part of a wider trend reported to federal cabinet by the Canadian Security and Intelligence Service in 2011, which warned that ethnic communities may be manipulated – sometimes through exploitation or coercion – to collect information on dissidents.

Xinjiang is a mineral- and oil-rich province that some Uyghurs refer to as East Turkestan. Located in China's west, the region of 22 million people is a tinderbox of ethnic tension between the Uyghurs and Han Chinese, who have flocked to the region for its economic promise and employment opportunities.

Human-rights reports say Uyghurs have been subject to inexplicable detention, religious persecution, disappearances and forced migration that activists characterize as a slow-burning form of ethnic cleansing.

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The People's Republic says that despite its best efforts to ease tensions, Xinjiang's unrest is part of a violent, separatist insurrection with ties to fanatical Islamic groups such as al-Qaeda. Nearly a year ago, a series of explosions in a crowded market in the regional capital, Urumqi, killed 39 people and left almost 100 others injured. Beijing has characterized the attack as the country's worst-ever act of terror.

Canada's most recognizable Uyghur is Huseyin Celil, a Burlington, Ont., resident who has been in a Chinese prison for nearly a decade on terrorism-related charges that Ottawa says it continues to dispute. China has refused to recognize his Canadian citizenship or permit this country's consular officials to visit him.

A Uyghur-Canadian who, in fear of his family's safety, did not want his real name disclosed, said Chinese internal security asked him to spy over the course of several recent visits to Xijiang, adding that he reported the incidents to Canada's Beijing embassy in 2013. On one trip, security services offered him money to set up a business. On another, they threatened to revoke his wife's visa to China. On still another occasion, he said he was threatened with treason charges.

"We can jail you any time we like," he recalled the authorities telling him. "We don't care about Canadian passports. This is China."

Kayum Masimov, president of the Uyghur Canadian Society, says the detaining of Canadians has led to suspicion and self-censoring in his community. "No one knows who to trust," he said.

Sitting in a downtown Montreal coffee shop with Mr. Masimov, a man who asked to be called Quttapay said he had trouble with the authorities more than a decade ago when someone reported him informally discussing the history of religion to students at a local university. At the station, officers tried to recruit Quttapay. They also warned him not to agitate against China back home and told him they were going to arrest him.

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Outraged, Quttapay dared the officers to go through with it. He was a Canadian, he told them. They'd wind up dealing with the Canadian government if they imprisoned him. At which point, the officers seized his passport. He was released, but then was informed he had to retrieve his document at another station. When he arrived there, authorities told him he had 48 hours to leave the country.

Another Uyghur with whom The Globe met, Bekkri (not his real name), wanted to leave China. An entrepreneur who lived in a Han-dominated Chinese megacity, Bekkri said Uyghurs were not welcome there. He had a travel visa, which the authorities knew about. But he also needed a Chinese passport, which Uyghurs say is easy for Han Chinese to obtain, but next to impossible for them. Police said he could have the passport, provided he spy for them. "Our people are there," he recalled a police officer telling him. "You can give them information."

A man of resources, Bekkri ultimately bribed officials with iPhones – eight of them – and got his passport under the table. Returning to China, he says, is out of the question: He'd be picked up immediately.

Another entrepreneur who didn't want his real name used, Yusup, told a similar story. Chinese officials offered to supply him with discounted goods and financial assistance should he wish to set up a store. "I'd make the worst spy," he told them. "I'll end up telling people what I'm doing even if I didn't want to."

The policeman seemed fine with his response. For the time being, at least. "Don't worry," he said. "We are patient."