Here is an excerpt from p. 174 of the 2002 edition of Inside Al-Qaeda by Rohan Gunaratna:

Today there are several Islamist groups in Xinjiang fighting for independence, and others have developed an extensive presence in Pakistan, Kazakhstan, Kyrgyzstan, and Germany, where funds are raised. Gradually, however, the ethno-nationalist character of the Uighurs' struggle has been overshadowed by Pan-Turkism and Pan-Islamism. The Islamist threat in Xinjiang manifested itself in a series of terrorist attacks against official targets there and even in Bejing, thus conforming to Al Qaeda's doctrine of striking the center instead of fighting in the periphery. Chinese officials investigating the Islamist support network in Kazakhstan and Kyrgyzstan have also been targeted ...

Of the two strategies adopted by the Chinese government to counter the spread of Islamism, one is to facilitate migration to Kyrgyzstan, but Kyrgyz of Chinese origin who served in Al Qaeda and the Taliban only became more determined to return to China to establish an Islamic state ... The spirit and determination of the Chinese Muslims remained undimmed and there are clear signs of the conflict escalating: in January 2002, an Uighur terrorist carried out another suicide mission in China, a tactic that was likely motivated by Al Qaeda indoctrination and training. Largely due to arrests in Xinjiang, the Chinese secret service has developed reasonably good intelligence on Al Qaeda, in particular its use of Hong Kong as a source of logistical procurement.

See also this primer on the East Turkestan Islamic Movement (ETIM), which I think has now folded back into the Islamic Movement of Uzbekistan (IMU) after both were heavily damaged by the US campaign in Afghanistan.