Islamic State (IS) is successfully recruiting Uyghurs to join its ranks.

China’s Global Times had previously reported that around 300 Chinese nationals were fighting alongside IS. Last September, the Iraqi Defense Ministry claimed to have captured a Chinese national involved in the fighting.

So far, however, the U.S. has had little luck convincing China to support its military operations against IS.

In the past, human rights groups have criticized China for not revealing specific information regarding alleged terrorist activity in Xinjiang.

Beijing, like government around the world, is concerned about its citizens joining up with IS and other extremist groups and then returning home to carry out attacks after receiving training and fighting experiences. Zhang’s remarks are the first public indication that this fear is becoming reality; extremists from Xinjiang are traveling to Iraq and Syria to join IS, and at least some have made it back home to China.

China is far from the only country having to worry about its citizens casting their lot with IS. In February, U.S. officials told the House Homeland Security Committee that IS has an estimated 20,000 foreign fighters from 90 countries, including 3,400 from Western countries. The officials believe that around 150 U.S. citizens have tried to join IS, although not all have made it to Iraq and Syria. A separate estimate from the Brookings Institution in November 2014 said at least 900 foreign fighters from France were now in Syria, with another 500 from the U.K. and between 300 and 500 from Germany (it should be noted, however, that many of these fighters may be affiliated with other militant groups in the region, rather than with IS in particular).

For its part, China has responded to this problem by stepping up border controls and cracking down on groups allegedly helping smuggle Uyghurs outside the country – including 10 Turkish citizens arrested in November for supplying false passports to Uyghurs. Beijing is also seeking increased law enforcement cooperation with countries known to serve as way stations for IS fighters, such as Turkey.

In his comments, Zhang emphasized that, compared to the rest of China, Xinjiang bears the brunt of the threat of terrorism and extremism. “Xinjiang also has to pay the price when extremists fight back,” Zhang said. Because of that, Zhang said, Xinjiang plays an outsized role in preventing the spread of terrorism to the rest of China. “The region has done a lot to ensure social stability in China,” Zhang said, pointing out that police officers in Xinjiang are 5.4 times more likely to be killed in the line of duty than their counterparts in the rest of China. The Diplomat