Q&A: China and the Uighurs
China's western Xinjiang region has a long history of discord between China's authorities and the indigenous Uighur ethnic minority.
Who are the Uighurs?
The Uighurs are Muslims. Their language is related to Turkish and they regard themselves as culturally and ethnically close to 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 famous 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 - a sprawling region that borders Central Asia - is now described by China as an autonomous region, like Tibet to its south.
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 in 2008.
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.
Uighurs have become a minority in Xinjiang due to this influx.
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, although 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. They were imprisoned at Guantanamo Bay for years without being charged with any offence and most have now been resettled elsewhere.
What sparked the 2009 riots?
Nearly 200 people died in ethnic riots in Urumqi, the administrative capital of Xinjiang, in July 2009. Officials said most of the dead were Han Chinese, but Uighur groups denied this.
One of the sparks for the violence seems to have been the deaths of two Uighurs in clashes with Han Chinese at a factory in southern China in June.
On 5 July 2009, Uighurs came out onto the streets of Urumqi to protest about these killings - but how and why these protests turned violent remains a contentious issue.
The authorities blame Xinjiang separatists based outside China for the unrest, and they singled out exiled Uighur leader Rebiya Kadeer, saying she incited the violence.
Rebiya Kadeer told the BBC she was not responsible for any of the violence.
Uighur exiles say police fired indiscriminately on peaceful protests - adding that this was what led to the violence and deaths.
What is the current situation in Xinjiang?
During China's economic boom, Xinjiang has received considerable state investment in industrial and energy projects that have in theory benefited the whole region.
China has been keen to highlight improvements made but many Uighurs complain that the Han are taking their jobs, and that their farmland has been confiscated for redevelopment.
The activities of local and foreign journalists are closely monitored by the Chinese state and there are few independent sources of news from the region.
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.
Analysts say only when the real culprits - poverty, marginalisation and discrimination - are defeated can the conflict be resolved.