Xinjiang is officially an autonomous region in China's west.

 Region is sparsely populated but has large reserves of oil, gas and minerals.

 Xinjiang was formerly a key transit point on the ancient Silk Road linking China to Europe.

 Region's Turkic speaking Uighur population number around eight million.

 Uighur activists say migration from other parts of China is part of official effort to dilute Uighur culture in their own land.

 Uighurs say they face repression on a range of fronts, including bans on the teaching of their language.

 Uighur separatists have staged series of low-level attacks since early 1990s.

 China says Uighur separatists are terrorists and linked to al-Qaeda.