As part of China's anti-corruption drive, its authorities have actively pursued alleged white-collar criminals far beyond its borders – and the response has not always been welcome.

Last summer, the Obama administration sent a stern warning to the Chinese government to stop covert activity on American soil.

Chinese secret agents are reportedly entering the United States on tourist and trade visas and then proceeding to pressure expatriates to return to China and face charges, according to The New York Times.

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Related: Chinese agents enter Canada on tourist visas to coerce return of fugitive expats

Related: Seven things to know about China's overseas anti-corruption campaign

Without extradition agreements with the United States, Canada and New Zealand – top destinations for fleeing Chinese economic fugitives – a zealous Chinese government keen to show its public that is cracking down on corruption is taking an aggressive approach.

Diplomatic dust-ups have also taken place between China and Australia over the presence of Chinese secret agents. A 2007 extradition treaty has yet to be ratified by Australia.

The anti-graft mission is a cornerstone of President Xi Jinping's rule. In 2013, he vowed to hunt down what he called "tigers" and "flies" – a vow to go after the country's most powerful leadership and its most minor bureaucrats.

Operation Fox Hunt, launched in 2014, saw the return of 700 suspected economic fugitives, and Operation Skynet, the renamed global operation in 2015, netted 857, according to China's public-security ministry.

The names, photos and charges against the 100 most-wanted were published in Chinese newspapers last year.

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They include bankers, local development officials and employees of state-run companies accused of engaging in fraud, bribery and embezzlement. Authorities in China believe that about a quarter of those individuals are in Canada.

How exactly China persuades alleged fugitives to return home is not entirely clear.

In 2014, a Shanghai publication offered clues about how agents with Operation Fox Hunt work. One police officer explained that repeated phone conversations with suspects did little to persuade them to return to China. Instead, a 20-minute face-to-face chat did the trick.

"My experience is that the effect of face-to-face persuasion and persuasion by telephone is totally different," Li Gongjing told Xinmin Weekly, according to Time Magazine.

The allegation by Western officials is that Chinese agents routinely use strong-arm tactics on foreign soil when dealing with expatriates.

China has bristled at criticism over its global campaign and argued that Western countries have been offering safe haven to individuals guilty of economic crimes.

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By pursuing extradition agreements with Western countries, China is looking to increase international co-operation on the return of alleged economic fugitives.

But there are significant concerns among human-rights groups over scant evidence of crimes and lack of due process in the Chinese justice system. There are also concerns that the courts could be used to settle political scores. An even greater worry is the use of torture and the death penalty.

With reports from wire services and Nathan VanderKlippe