(And notice the bias in this article's title: "China blames Muslim extremists" rather than "Muslims kill again in Xinjiang.")
From here:
Captured suspects confessed that their ringleaders had earlier fled to Pakistan and joined the separatist "East Turkestan Islamic Movement," and received training in making firearms and explosives before infiltrating back into China, the Kashgar government said.
"The members of this group all adhere to extremist religious ideas and adamantly support Jihad," said the statement, referring to the Arabic term for struggle used by advocates of militant Islam to describe their cause.