China regards militants from its Uighur minority as a major threat to security at the 2008 Olympic Games in Beijing.
The militants are blamed for a bloody attack on a border post in western China in the run-up to the Games. Human rights groups have long accused China of persecuting the Uighurs.
Who are the Uighurs?
The Uighurs are Muslims based in north-western China's Xinjiang region. Their language is related to Turkish and they regard themselves as culturally and ethnically close to other Central Asian nations.
The region's economy has for centuries revolved around agriculture and trade, with towns such as Kashgar thriving as hubs along the Silk Road.
In the early part of the 20th Century, the Uighurs briefly declared independence. The region was brought under the complete control of communist China in 1949.
Officially, Xinjiang is now described by China as an autonomous region, like Tibet to its south.
What are China's concerns about the Uighurs?
Beijing says Uighur militants have been waging a violent campaign for an independent state by plotting bombings, sabotage and civic unrest.
Since the 9/11 attacks in the US, China has increasingly portrayed its Uighur separatists as auxiliaries of al-Qaeda.
It has accused them of receiving training and indoctrination from Islamist militants in neighbouring Afghanistan.
However, little public evidence has been produced in support of these claims.
More than 20 Uighurs were captured by the US military after its invasion of Afghanistan. Though imprisoned at Guantanamo Bay for six years, they have yet to be charged with any offence.
What complaints have been made against the Chinese in Xinjiang?
Activists say the Uighurs' religious, commercial and cultural activities have been gradually curtailed by the Chinese state.
China is accused of intensifying its crackdown on the Uighurs after street protests in the 1990s - and again, in the run-up to the Beijing Olympics.
Over the past decade, many prominent Uighurs have been imprisoned or have sought asylum abroad after being accused of terrorism.
China is said to have exaggerated the threat from Uighur separatists in order to justify repression in the region.
Beijing has also been accused of seeking to dilute Uighur influence by arranging the mass immigration of Han Chinese, the country's majority ethnic group, to Xinjiang.
Han Chinese currently account for roughly 40% of Xinjiang's population.
What is the current situation in Xinjiang?
Over the last decade, major development projects have brought prosperity to Xinjiang's big cities.
The activities of local and foreign journalists in the region are closely monitored by the Chinese state and there are few independent sources of news from the region.
China has been keen to highlight improvements made to the region's economy while Uighurs interviewed by the press have avoided criticising Beijing.
However, occasional attacks on Chinese targets suggest Uighur separatism remains a potent - and potentially violent - force.