During the Syrian civil war, a Chinese hostage was murdered by the Islamic State, which claimed its desire to fight against China over Xinjiang.[319] These militants are also very active in Syria, mostly Idlib, where it formed to be one of the most radical fighting groups in the conflict, which prompted China to take cautious reactions.[320][321]

A number of Uyghur militants have been recruited by ISIS[322][323] and have had a presence in Southeast Asia, with some joining Mujahidin Indonesia Timor.[324]

Some nice context for the confused here.