China is not immune to the pervasive fear in Western security circles that as ISIS collapses in the Middle East, trained and battle-hardened foreign fighters will return to motherland to launch attacks at home, according to a local news report.

Citing government and diplomatic sources, the South China Morning Post reported that the number of "trained jihadist fighters" intercepted at the Chinese border has risen significantly in the past year and that the threat of terrorist attacks was serious. In May 2017, Syria's Ambassador to China, Imad Moustapha, estimated that as many as 5,000 Chinese, mostly Uighurs from China's western Xinjiang province, were believed to have gone to Syria for to fight for various militant groups (though other estimates put the number far lower).

"China as well as every other country should be extremely concerned," Moustapha told Reuters.

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Western security officials have long feared what former FBI Director James Comey called a terrorist "diaspora."

"The returning terrorist fighter threat... is what we are watching very closely," Comey told lawmakers in October 2015. "We see the logic of it telling us that [there] will be a problem for the next five years plus, because not every terrorist will get killed on the battlefield in Syria or Iraq. Inevitably, there will be a diaspora."

At that time, it was estimated that some 250 Americans and thousands of Western Europeans had either gone to Iraq or Syria or had attempted to travel there to join the fighting.

Last month, Iraq declared victory over ISIS. It was a development Colin Clarke, a political scientist at The RAND Corporation, had predicted would "create uncertainty, rising threats, opportunities for extremists, and new challenges for our military, intelligence and law enforcement communities."

Clarke noted that not all returnees will be dangerous, as some would be disillusioned with the terror group, but many would be unlikely to deradicalize on their own. In China, he wrote later, there was even less hope for deradicalization "if [the returnees] are continuously provoked or oppressed by Chinese government authorities."

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"With no known reintegration programs or official policies offered by the Chinese government for former terrorists or separatists, this pathway [to deradicalization] seems unlikely," he wrote.

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